Upgrade Avalonia to 12 and add .NET 10 support

.nuke/build.schema.json

@@ -0,0 +1,128 @@
+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "definitions": {
+    "Host": {
+      "type": "string",
+      "enum": [
+        "AppVeyor",
+        "AzurePipelines",
+        "Bamboo",
+        "Bitbucket",
+        "Bitrise",
+        "GitHubActions",
+        "GitLab",
+        "Jenkins",
+        "Rider",
+        "SpaceAutomation",
+        "TeamCity",
+        "Terminal",
+        "TravisCI",
+        "VisualStudio",
+        "VSCode"
+      ]
+    },
+    "ExecutableTarget": {
+      "type": "string",
+      "enum": [
+        "CiAzureWindows",
+        "Clean",
+        "Compile",
+        "CreateIntermediateNugetPackages",
+        "CreateNugetPackages",
+        "Restore"
+      ]
+    },
+    "Verbosity": {
+      "type": "string",
+      "description": "",
+      "enum": [
+        "Verbose",
+        "Normal",
+        "Minimal",
+        "Quiet"
+      ]
+    },
+    "NukeBuild": {
+      "properties": {
+        "Continue": {
+          "type": "boolean",
+          "description": "Indicates to continue a previously failed build attempt"
+        },
+        "Help": {
+          "type": "boolean",
+          "description": "Shows the help text for this build assembly"
+        },
+        "Host": {
+          "description": "Host for execution. Default is 'automatic'",
+          "$ref": "#/definitions/Host"
+        },
+        "NoLogo": {
+          "type": "boolean",
+          "description": "Disables displaying the NUKE logo"
+        },
+        "Partition": {
+          "type": "string",
+          "description": "Partition to use on CI"
+        },
+        "Plan": {
+          "type": "boolean",
+          "description": "Shows the execution plan (HTML)"
+        },
+        "Profile": {
+          "type": "array",
+          "description": "Defines the profiles to load",
+          "items": {
+            "type": "string"
+          }
+        },
+        "Root": {
+          "type": "string",
+          "description": "Root directory during build execution"
+        },
+        "Skip": {
+          "type": "array",
+          "description": "List of targets to be skipped. Empty list skips all dependencies",
+          "items": {
+            "$ref": "#/definitions/ExecutableTarget"
+          }
+        },
+        "Target": {
+          "type": "array",
+          "description": "List of targets to be invoked. Default is '{default_target}'",
+          "items": {
+            "$ref": "#/definitions/ExecutableTarget"
+          }
+        },
+        "Verbosity": {
+          "description": "Logging verbosity during build execution. Default is 'Normal'",
+          "$ref": "#/definitions/Verbosity"
+        }
+      }
+    }
+  },
+  "allOf": [
+    {
+      "properties": {
+        "Configuration": {
+          "type": "string",
+          "description": "configuration"
+        },
+        "ForceNugetVersion": {
+          "type": "string",
+          "description": "force-nuget-version"
+        },
+        "SkipTests": {
+          "type": "boolean",
+          "description": "skip-tests"
+        },
+        "Solution": {
+          "type": "string",
+          "description": "Path to a solution file that is automatically loaded"
+        }
+      }
+    },
+    {
+      "$ref": "#/definitions/NukeBuild"
+    }
+  ]
+}

.nuke/parameters.json

@@ -0,0 +1,4 @@
+{
+  "$schema": "./build.schema.json",
+  "Solution": "src/AvalonStudio.Shell.sln"
+}

.planning/codebase/CONVENTIONS.md

@@ -0,0 +1,107 @@
+# Coding Conventions
+
+**Analysis Date:** 2026-08-28
+
+## Naming Patterns
+
+**Files:**
+- Use PascalCase C# filenames that name the primary type: `src/AvalonStudio.Shell.Extensibility/Commands/CommandService.cs`, `src/AvalonStudio.Shell/Controls/StatusBarViewModel.cs`, and `src/ShellExampleApp/MainWindowViewModel.cs`.
+- Pair Avalonia views with their code-behind using the same basename (for example, `src/ShellExampleApp/MainWindow.xaml` and `src/ShellExampleApp/MainWindow.xaml.cs`). Several reusable shell resources use the legacy `.paml.cs` suffix, such as `src/AvalonStudio.Shell/ShellView.paml.cs` and `src/AvalonStudio.Shell/Controls/StatusBar.paml.cs`; retain the existing suffix when extending those resources.
+- Place types in a directory corresponding to their concern and namespace segment, such as `MVVM`, `Commands`, `Menus`, `Docking`, `Converters`, or `Behaviors` beneath `src/AvalonStudio.Shell.Extensibility/`.
+
+**Functions:**
+- Use PascalCase for public, protected, and private methods (`GetMainMenu`, `ResolveCommands`, `LoadLayout`) in `src/AvalonStudio.Shell.Extensibility/MainMenu/MainMenuService.cs` and `src/AvalonStudio.Shell/ShellViewModel.cs`.
+- Use `On...` for lifecycle hooks and event-style methods, including `OnOpen`, `OnClose`, `OnSelected`, and `OnFrameworkInitializationCompleted` in `src/AvalonStudio.Shell.Extensibility/Documents/GenericDocumentTabViewModel.cs` and `src/ShellExampleApp/App.paml.cs`.
+- Use verb-led extension methods such as `Dock`, `AddOrSelectDocument`, and `GetOrCreate` in `src/AvalonStudio.Shell/DockExtensions.cs` and `src/AvalonStudio.Shell.Extensibility/Shell/IShellExtensions.cs`.
+
+**Variables:**
+- Use camelCase for parameters, local variables, and pattern variables (`commandSettings`, `parentItem`, `activatable`) throughout `src/AvalonStudio.Shell.Extensibility/Commands/CommandService.cs`.
+- Use private camelCase fields in most UI/view-model code (`_documents`, `_viewModel`, `modalDialog`) as in `src/AvalonStudio.Shell/ShellViewModel.cs`; legacy and binding-oriented classes also use non-underscore fields (`lineNumber`, `isVisible`) in `src/AvalonStudio.Shell/Controls/StatusBarViewModel.cs` and `src/AvalonStudio.Shell.Extensibility/Dialogs/ModalDialogViewModelBase.cs`. Follow the surrounding file's field style instead of mixing both conventions.
+- Use the `s_` prefix for private static mutable fields, as in `s_compositionHost` in `src/AvalonStudio.Shell.Extensibility/IoC.cs`.
+
+**Types:**
+- Use PascalCase for classes, interfaces, enums, attributes, and generic parameters. Prefix interfaces with `I` (`IShell`, `IMenuItemFactory`, `IObservableCollection<T>`) in `src/AvalonStudio.Shell.Extensibility/Shell/IShell.cs`, `src/AvalonStudio.Shell.Extensibility/Menus/IMenuItemFactory.cs`, and `src/AvalonStudio.Shell.Extensibility/MVVM/IObservableCollection.cs`.
+- Name UI state classes with `ViewModel`, controls/views with `View`, and MEF attribute types with `Export...Attribute`, matching `src/AvalonStudio.Shell/Controls/StatusBarViewModel.cs` and `src/AvalonStudio.Shell.Extensibility/Commands/ExportCommandDefinitionAttribute.cs`.
+
+## Code Style
+
+**Formatting:**
+- No repository-root formatter configuration is detected. The only editor configuration is `build/.editorconfig`, so it applies to the build project rather than the `src/` projects.
+- In `build/.editorconfig`, omit redundant `this.` qualification and prefer expression-bodied properties, indexers, and accessors. It explicitly permits omitted accessibility modifiers (`dotnet_style_require_accessibility_modifiers = never`).
+- Use block-scoped namespaces. Every production C# sample uses `namespace ... { ... }`, for example `src/AvalonStudio.Shell/CompositionRoot.cs` and `Numerge/Numerge/NugetPackageMerger.cs`.
+- Place opening braces on a new line. Preserve the local indentation of the file: the repository contains both spaces and tabs, notably tabs in `src/AvalonStudio.Shell.Extensibility/Commands/CommandService.cs` and spaces in `src/AvalonStudio.Shell.Extensibility/MainMenu/MainMenuService.cs`.
+- Prefer concise expression-bodied members where already established (`Title => Platform.AppName` in `src/AvalonStudio.Shell/ShellViewModel.cs` and `BuildAvaloniaApp() => ...` in `src/ShellExampleApp/App.paml.cs`); use full accessors when setters contain notification or guard logic.
+
+**Linting:**
+- No project-level analyzer, lint task, `TreatWarningsAsErrors`, `Nullable`, or `LangVersion` configuration is detected in the `.csproj` files or CI pipeline.
+- `build/.editorconfig` sets the listed style diagnostics to warning severity. Do not assume additional analyzer enforcement.
+
+## Import Organization
+
+**Order:**
+1. Avalonia, Dock, ReactiveUI, and other framework imports are commonly placed first.
+2. `AvalonStudio.*` project imports generally follow.
+3. `System.*` imports occur last in many UI files, including `src/AvalonStudio.Shell/ShellViewModel.cs` and `src/ShellExampleApp/Commands/ThemeCommands.cs`.
+
+- Import ordering is not mechanically consistent: `src/AvalonStudio.Shell/CompositionRoot.cs` starts with project imports while `src/AvalonStudio.Shell.Extensibility/Commands/CommandService.cs` starts with `System.*`. Keep imports explicit and preserve the grouping/order of the file being modified; do not introduce a new sorting rule in an isolated change.
+- Use direct namespaces rather than a repository-wide global-using mechanism. Static imports are limited to build orchestration in `build/Build.cs`.
+
+**Path Aliases:**
+- Not applicable. C# projects reference namespaces directly; no alias/import configuration is detected.
+
+## Error Handling
+
+**Patterns:**
+- Let ordinary framework and programming errors propagate. Most public methods do not wrap exceptions, including layout and menu construction in `src/AvalonStudio.Shell/ShellViewModel.cs` and `src/AvalonStudio.Shell.Extensibility/MainMenu/MainMenuService.cs`.
+- Catch only a failure with a defined recovery result. `Numerge/Numerge/NugetPackageMerger.cs` catches `MergeAbortedException`, logs its message, and returns `false`; callers in `build/Build.cs` convert `false` to a build failure.
+- At extension-discovery boundaries, catch broad load errors and continue loading remaining components, emitting diagnostic text through `System.Console.WriteLine` as in `src/AvalonStudio.Shell/CompositionRoot.cs`.
+- Service lookup treats unavailable optional exports as absence: `src/AvalonStudio.Shell.Extensibility/IoC.cs` returns `default` for single lookups and `Enumerable.Empty<T>()` for plural lookup. Callers must safely handle a missing export.
+- Use early null guards for optional arguments, as in `RemoveDocument` in `src/AvalonStudio.Shell/ShellViewModel.cs`; avoid adding broad catch-and-ignore blocks.
+
+## Logging
+
+**Framework:** console and Nuke build logging; no application logging abstraction is detected.
+
+**Patterns:**
+- Use `Information(...)` for build diagnostics in `build/Build.cs`.
+- `Numerge/Numerge/INumergeLogger.cs` defines `Info`, `Error`, and `Warning` for package-merge work; pass an `INumergeLogger` into merger operations rather than writing directly from that library.
+- Use `System.Console.WriteLine` only for extension-loading diagnostics in `src/AvalonStudio.Shell/CompositionRoot.cs`. No structured logging provider is configured for shell runtime code.
+
+## Comments
+
+**When to Comment:**
+- Comment non-obvious platform, plugin, or framework constraints. `src/AvalonStudio.Shell/CompositionRoot.cs` documents why its custom `AppDomain` loader remains, and `src/AvalonStudio.Shell.Extensibility/MainMenu/MainMenuService.cs` explains the menu-parent registration rule.
+- Preserve targeted suppression comments where required, such as the ReSharper suppressions at the top of `Numerge/Numerge/NugetPackageMerger.cs`; do not add blanket suppression files.
+- TODO comments exist for explicit pending work (for example `src/AvalonStudio.Shell/CompositionRoot.cs` and `src/AvalonStudio.Shell.Extensibility/Commands/CommandService.cs`). Keep a TODO adjacent to the constrained behavior and describe the intended outcome.
+
+**JSDoc/TSDoc:**
+- Use XML documentation for reusable public/protected collection and framework-extension behavior. `src/AvalonStudio.Shell.Extensibility/MVVM/BindableCollection.cs` documents overridden collection operations and their parameters with `/// <summary>` and `/// <param>`.
+- Small view models, services, and straightforward public models generally have no XML comments; avoid redundant documentation for self-evident members.
+
+## Function Design
+
+**Size:**
+- Small helpers and model members are preferred, but orchestration classes may own longer stateful flows: `src/AvalonStudio.Shell/ShellViewModel.cs` manages shell lifecycle and docking, and `src/AvalonStudio.Shell.Extensibility/MainMenu/MainMenuService.cs` builds menu trees. Keep UI state transitions with the owning view model/service rather than creating ad-hoc utility classes.
+
+**Parameters:**
+- Use constructor injection with `[ImportingConstructor]` for MEF-composed services (`src/AvalonStudio.Shell.Extensibility/Commands/CommandService.cs` and `src/AvalonStudio.Shell.Extensibility/MainMenu/MainMenuService.cs`).
+- Use optional parameters for feature toggles/default UI behavior (`AddDocument(..., bool temporary = false, bool select = true)` in `src/AvalonStudio.Shell/ShellViewModel.cs`) and generic constraints for document/type factories in the same file.
+
+**Return Values:**
+- Return immutable/read-only views of owned mutable state when exposing collections (`Documents => _documents.AsReadOnly()` in `src/AvalonStudio.Shell/ShellViewModel.cs`).
+- Return `bool` for expected operation success/failure in the Numerge merge layer (`Numerge/Numerge/NugetPackageMerger.cs`); use exceptions for unrecoverable build failure in `build/Build.cs`.
+- For reactive UI properties, update backing fields through `RaiseAndSetIfChanged` or explicitly raise dependent property notifications, following `src/AvalonStudio.Shell/Controls/StatusBarViewModel.cs`.
+
+## Module Design
+
+**Exports:**
+- Use one primary public type per PascalCase file. Keep closely coupled helpers/implementations together when they are internal, such as the tab classes in `src/AvalonStudio.Shell/DockExtensions.cs`.
+- Expose extension points through interfaces and MEF attributes: `src/AvalonStudio.Shell.Extensibility/Shell/IShell.cs`, `src/AvalonStudio.Shell.Extensibility/Commands/ExportCommandDefinitionAttribute.cs`, and `[Export]/[Shared]` services in `src/AvalonStudio.Shell.Extensibility/Commands/CommandService.cs`.
+- Use `internal` for example-app registration holders that should not form public API, as in `src/ShellExampleApp/Commands/ThemeCommands.cs` and `src/ShellExampleApp/MainMenu/ThemeMainMenuItem.cs`.
+
+**Barrel Files:**
+- Not applicable. No C# barrel/export-aggregator files are detected; consumers import the concrete namespace/type they need.
+
+---
+
+*Convention analysis: 2026-08-28*

.planning/codebase/INTEGRATIONS.md

@@ -0,0 +1,89 @@
+# External Integrations
+
+**Analysis Date:** 2026-08-28
+
+## APIs & External Services
+
+**Package distribution:**
+- NuGet.org - package restore source for the .NET solution.
+  - SDK/Client: .NET SDK/NuGet invoked by `DotNetRestore` in `build/Build.cs`.
+  - Auth: not configured in `src/nuget.config`; it contains only the public `nuget.org` source.
+
+**Source control and versioning:**
+- Git/GitHub repository metadata - NUKE identifies the canonical repository and uses GitVersion metadata during builds.
+  - SDK/Client: `Nuke.Common` 8.1.4 and `GitVersion.Tool` 6.8.2 in `build/_build.csproj`.
+  - Auth: not handled by application code; CI checkout credentials are platform-managed.
+
+**CI service:**
+- Azure Pipelines - builds every branch/tag on `windows-latest`, installs .NET SDK 8 and 10, runs the NUKE target, and publishes NuGet artifacts.
+  - SDK/Client: Azure Pipelines YAML tasks in `azure-pipelines.yml`; CI-state detection via `Nuke.Common.CI.AzurePipelines` in `build/BuildParameters.cs`.
+  - Auth: Azure Pipelines managed identity/token configuration is not defined in this repository.
+
+**Desktop extension boundary:**
+- Local MEF extensions - the application discovers `extension.json` manifests under the executable's `Extensions` directory, then loads declared `mefComponents` assemblies.
+  - SDK/Client: `System.Composition` in `src/AvalonStudio.Shell/CompositionRoot.cs` and `src/AvalonStudio.Shell/ExtensionManager.cs`.
+  - Auth: none; extensions are filesystem-local rather than a remote API.
+
+No HTTP clients, third-party SaaS SDKs, payment services, messaging providers, or outbound application API calls are detected in `src/`.
+
+## Data Storage
+
+**Databases:**
+- Not detected. No ORM, database client, connection string, or database configuration is present in `src/`.
+
+**File Storage:**
+- Local filesystem only. The platform initialises a per-application base directory, `Settings` directory, and executable-relative `Extensions` directory in `src/AvalonStudio.Shell.Extensibility/Platforms/Platform.cs`.
+- `GlobalSettings.json` is read and written via `src/AvalonStudio.Shell.Extensibility/GlobalSettings/GlobalSettings.cs`.
+- `CommandSettings.json` is read and written via `src/AvalonStudio.Shell.Extensibility/Commands/Settings/CommandSettingsService.cs`.
+- Extension manifests are parsed from local `extension.json` files by `src/AvalonStudio.Shell/ExtensionManifest.cs`.
+- Client: `Newtonsoft.Json` 13.0.3 through the shared serializer in `src/AvalonStudio.Shell.Extensibility/Utils/SerializedObject.cs`.
+
+**Caching:**
+- Local application storage only. `AVALON_CACHE_PATH` can relocate the base directory; no distributed cache is configured.
+
+## Authentication & Identity
+
+**Auth Provider:**
+- Not detected. `src/` contains no authentication, authorization, OAuth/OpenID, JWT, or identity-provider integration.
+  - Implementation: not applicable.
+
+## Monitoring & Observability
+
+**Error Tracking:**
+- None detected. No error-tracking SDK or telemetry service is referenced by the project files or source.
+
+**Logs:**
+- The extension loader writes component-load failures to standard console output in `src/AvalonStudio.Shell/CompositionRoot.cs`.
+- NUKE writes build diagnostics through its logging API in `build/Build.cs`; no structured or remote log sink is configured.
+
+## CI/CD & Deployment
+
+**Hosting:**
+- Not applicable. This is a desktop-library and NuGet-package repository, not a hosted service.
+
+**CI Pipeline:**
+- Azure Pipelines configuration in `azure-pipelines.yml` executes `CiAzureWindows` from `build/Build.cs` and uploads `artifacts/nuget` as a pipeline artifact.
+- Packaging is local to the build agent: `build/Build.cs` restores, compiles, packs, and merges packages. No NuGet feed push/publish task is configured.
+
+## Environment Configuration
+
+**Required env vars:**
+- None for normal application startup.
+- Optional `AVALON_CACHE_PATH` overrides the runtime settings base path in `src/AvalonStudio.Shell.Extensibility/Platforms/Platform.cs`.
+- Azure builds expect the non-secret `BUILD_BUILDID` CI variable when generating CI prerelease versions in `build/BuildParameters.cs`.
+
+**Secrets location:**
+- No repository-managed secret file or secret-store integration is detected. No `.env` file is present.
+- CI and source-control authentication, if needed, remain external to repository code and configuration.
+
+## Webhooks & Callbacks
+
+**Incoming:**
+- None detected. The repository contains no web server, endpoint, or webhook handler.
+
+**Outgoing:**
+- None detected from application code. The CI pipeline publishes artifacts to Azure Pipelines; it does not define application callbacks.
+
+---
+
+*Integration audit: 2026-08-28*