feat(avalonia): migrate Connect and Deploy from WPF

[mchave3]

Summary

Migrates Foundry Connect and Foundry Deploy from WPF to Avalonia through sequential, independently reviewed waves. No WPF runtime fallback will be shipped.

This umbrella PR remains a draft until both applications, packaging, WinPE validation, accessibility, localization, and release cutover gates are complete.

Reason

The migration replaces the Windows-only WPF presentation layer while preserving the existing domain behavior, executable identities, configuration contracts, telemetry, logging, deployment orchestration, and WinPE boot-media behavior. The new interface follows the approved modern, focused deployment experience.

Current changes

Wave 1 is integrated and provides:

• shared Foundry.Avalonia presentation library and headless test project
• Avalonia packages pinned directly to 12.1.1 in their owning project files
• semantic light and dark resources
• Full, Reduced, and None motion policies
• adaptive compact, standard, and wide layouts
• UI dispatcher and timer adapters
• reusable shell, utility, status, information-grid, progress, and read-only dialog controls
• licensed Fluent UI System Icon vectors with pinned provenance
• architecture-boundary and headless visual tests, including RTL and 200% scaling

Remaining migration waves

• make Connect core behavior framework-neutral
• replace the Connect WPF shell and views with Avalonia
• make Deploy scheduling, confirmation, and presentation contracts framework-neutral
• replace the Deploy WPF shell, wizard, progress, success, error, and Tools experiences with Avalonia
• update WinPE payload provisioning, release automation, validation, and documentation
• remove every superseded WPF source, resource, package, and runtime dependency in its replacement wave

Current validation

• dotnet restore src/Foundry.slnx
• x64 full solution build: 0 errors; 164 existing warnings
• x64 full solution tests: 1,107 passed; 0 failed
• ARM64 Foundry.Avalonia cross-build: 0 warnings; 0 errors
• ARM64 runtime tests were not run because no ARM64 test system is available
• local planning files and generated visual-review frames are not tracked or included
• CI was not awaited

Merge gates

This PR must remain draft until:

• Connect is WPF-free and passes desktop, headless, packaging, real x64 WinPE, and static ARM64 package validation
• Deploy is WPF-free and passes desktop, headless, packaging, destructive-operation, real x64 WinPE, static ARM64 package, and post-reboot validation
• release workflows publish the existing application identities as complete multi-file Avalonia payloads
• repository checks reject production WPF usage in Connect and Deploy
• accessibility, localization, RTL, scaling, diagnostics redaction, telemetry, and documentation gates pass