Avalonia test runner: UI revamp

[xen2]

Avalonia test runner: UI revamp

Rebuilds the interactive test runner (Avalonia window shown when a Stride test exe is launched with STRIDE_TESTS_INTERACTIVE=1).

Highlights

• Filter textbox (auto-focused) + status chips (All / Passed / Failed / Skipped / Not run) with live counts.
• Per-row run buttons: test mode (gold compare diff) & interactive run (preview only, doesn't close window)
• Re-run failed + Run filtered/selected with Ctrl+R / F5 shortcuts.
• Multi-select in the tree.
• Save image checkbox (forces save on success) and RenderDoc capture-mode dropdown (Never / On error / Always).
• Inspect pane: failure message + stack trace + live-streamed stdout/stderr with Warning: / Error: tinting.
• Summary bar with running pass/fail/skip totals and elapsed time.
• Keyboard nav: / or Ctrl+F to focus filter, Esc to clear, Up/Down/PageUp/PageDown from the filter to navigate the tree, Enter / Shift+Enter to run / preview.
• Dark theme + responsive layout (toolbar wraps, main split flips vertical on narrow / portrait viewports).

A screenshot is worth a thousand words:

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My change requires a change to the documentation.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have built and run the editor to try this change out.

[github-actions]

🤖 Draft PR — automatic CI is skipped to save runner minutes.

• /ci main — what would auto-run if this PR weren't draft
• /ci all — main + screenshot regression (/ci e2e)
• /ci help — full list, per-platform and per-suite

Marking ready-for-review re-enables full CI automatically.

[Kryptos-FR]

This should use a color from the theme so that if the users prefers a light theme it picks the corresponding background color. Or no color as I think the theme as one by default.

[Kryptos-FR]

Should probably be Default instead so that it follows the system theme.