feat(connect): migrate Foundry Connect to Avalonia

[mchave3]

Summary

Migrate Foundry Connect from WPF to Avalonia while preserving its WinPE network-readiness and handoff contracts.

Reason

Wave 3 removes the WPF presentation layer and delivers the approved adaptive, accessible Connect experience on the shared Avalonia foundation.

Main changes

• replace the WPF application shell, readiness views, Wi-Fi flows, menus, About, and diagnostics with Avalonia
• add compact, standard, wide, RTL, scaling, motion, localization, accessibility, and headless visual coverage
• preserve Ethernet, provisioned Wi-Fi, discovered Wi-Fi, exit-code, and automatic-continue behavior
• publish Connect as a self-contained, untrimmed, multi-file payload with deterministic manifests and architecture/WPF validation
• keep Deploy on its existing packaging contract until its owning migration wave

Testing

• dotnet test src/Foundry.slnx -c Debug -p:Platform=x64 --nologo (1,174 passed)
• pwsh ./scripts/Publish-FoundryConnect.ps1 -Configuration Release -AllRuntimes
• validated win-x64 and win-arm64 payloads (321 files each); ARM64 was not executed
• package graph and source scan show no WPF presentation dependency in Foundry.Connect

CI was not awaited per migration workflow.