Use MarkView.Avalonia library for markdown

Captures the full delta between the current Avalonia branch and the WPF
launcher on master — including silent regressions that are not marked
with TODO/FIXME — and a phased roadmap to close the gap for
cross-platform parity. Notes Stride.Metrics and PrivacyPolicyHelper as
deliberate, permanent removals.

…ncher port roadmap

Adds a test-infrastructure phase covering bootstrap of Stride.Launcher.Tests,
view-model and Avalonia-headless integration tests, and CI wiring for both
Windows and Linux.

…n flow

…rsistence proposal

…Settings

…ct rows

…wn ViewModelBase

Copies the ViewModelBase implementation from Stride.Core.Presentation (minus
IDestroyable/IViewModelServiceProvider) so the runner has no external MVVM
dependency. Renames SetProperty → SetValue to match Stride's API.

System.Drawing.Common was previously imported as a dependency for Avalonia.

…uncement panels

- Root Grid gains ClipToBounds="True" so panels are hidden while off-screen.
- Release-notes Grid: IsVisible replaced by Classes.visible + TransformOperationsTransition
  (translateX(2000px) → translateX(0), 1s CubicEaseOut). Selector anchored to class
  rn-slide to prevent descendant Grids from inheriting the transform.
- Release-notes header: empty Button/TextBlock stubs replaced with a working close
  button (ActiveReleaseNotes.ToggleCommand) and a version title TextBlock.
- Release-notes content Grid gains Margin="{StaticResource BorderThicknessTile}" (12px)
  to match master's TileBorderThickness spacing.
- Release-notes DockPanel gains BackgroundTileAlpha background (matches master's
  TileAlphaBackgroundBrush = #C0434343).
- Announcement Border: IsVisible replaced by Classes.visible + same transition approach,
  selector anchored to class ann-slide.
- docs: mark Phase 3 items complete in port-status.md; correct two pre-existing
  entries (CurrentToolTip and StaysOpenContextMenu) that were already implemented.

Master rewrote URLs ending in .md to .html before opening so docs links
resolve to rendered pages instead of raw markdown source.

…ttingsService wrapper

…sService

…behind to ILauncherSettingsService

…, TryCloseAsync)

…Service in port-status

The commented-out RevokeAllPrivacyPolicy() call in UninstallAsync was a
placeholder from the WPF-to-Avalonia port. Telemetry and the privacy-policy
consent flow were permanently removed when the port started, so any residual
registry keys or settings files left by the old WPF launcher are harmless
orphans that do not need to be scrubbed.

- Remove the commented line and its FIXME: xplat-launcher marker (Launcher.cs)
- Update cross-platform.md: drop the 'keep it for now' note
- Update port-status.md: mark Phase 2 item 4 closed; update the
  Deliberate changes table row for privacy policy

…pleted is intentional

MinimalApp.OnFrameworkInitializationCompleted is empty by design: the
crash-report and already-running-instance dialog paths in Launcher.cs
each construct and wire their window directly inside their own AppMain
callback, so no framework-level initialisation (no MainViewModel, no
markdown pipeline, no services) is needed.

- Update 'Features removed without a replacement' section to explain the
  design rather than flag it as a concern
- Close Phase 2 item 3 ('Review MinimalApp paths')

… right-click offset

Right-click events on the Button inside each row were not reliably bubbling up
to the outer Border's ContextMenu on Linux. Moving the ContextMenu to the Button
directly — and adding VerticalAlignment="Stretch" — ensures the menu opens wherever
the row is visually hit-tested.

- Mark 'Show in Explorer' as fixed (cross-platform since commit c2555d0):
  update 'already ported' bullet and strike through the regression entry
  with the three-platform implementation detail
- Correct slide animation duration from 0.5s to 1s in both the Fixed
  description and the Phase 3 roadmap entries (1s was intentional)