feat(clients/windows): WinUI UX batch - tile hover, Settings NavigationView, modal slide-up

Bump windows-reactor + windows to a4f7b2cb (from b4129fcc) for the new
PointerEntered/PointerExited events; migration is mechanical renames only
(SymbolGlyph->Symbol, placeholder->placeholder_text, on_changed->
on_text_changed/on_toggled, on_menu_item_clicked->on_item_clicked,
on_ready->on_mounted). New runtime model: reactor lost its build.rs, so the
client build.rs stages the WinAppSDK bootstrap via
windows-reactor-setup::as_framework_dependent() and main calls
windows_reactor::bootstrap() (missing either = 0x80040154 at launch);
staged filenames unchanged, so pack-msix and the MSIX manifest are untouched.

- Host tiles: WinUI pointer-over fill (ControlFillSecondary) via the new
  pointer enter/exit events, hover id in root state (backend-wired handlers
  bypass the reconciler flush, like the flyout clicks).
- Settings: stock NavigationView sidebar (Windows-Settings pattern) with
  Display/Video/Input/Audio/About panes, built-in back arrow, wide content
  column, and a per-section content slide-up tween. The section card is
  KEYED by section: an in-place diff across sections re-sets a reused
  ComboBox's items (clearing WinUI's selection) but skips selected_index
  when the values compare equal, rendering a blank selection - the key
  forces a remount. Card titles/descriptions dropped; per-control guidance
  moved to hover tooltips (ToolTipService).
- New "Show the stats overlay (HUD)" setting (show_hud, default on),
  honored mid-stream via the 400 ms HUD re-render.
- Add-host modal: entrance fade + slide-up tween (scrim fades with it).
- Self-initiated disconnect (Ctrl+Alt+Shift+D -> Ended(None)) returns to
  the host list silently instead of raising the error banner.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/windows/packaging/README.md

@@ -22,7 +22,7 @@ stamps the manifest `ProcessorArchitecture` and names the output. See
 | File | Source |
 |---|---|
 | `punktfunk-client.exe` | the release build |
-| `Microsoft.WindowsAppRuntime.Bootstrap.dll`, `resources.pri` | auto-staged by windows-reactor's `build.rs` |
+| `Microsoft.WindowsAppRuntime.Bootstrap.dll`, `resources.pri` | staged by the client's `build.rs` via `windows-reactor-setup::as_framework_dependent()` |
 | `SDL3.dll` | auto-staged by the `sdl3` crate |
 | `avcodec/avformat/avutil/swscale/swresample/...-*.dll` | `FFMPEG_DIR\bin` |
 | `Assets\*.png` | checked-in tile/store logos (rasterized from `packaging/flatpak/io.unom.Punktfunk.svg`) |
@@ -30,12 +30,13 @@ stamps the manifest `ProcessorArchitecture` and names the output. See
 
 ### Why an "unpackaged" WinUI app packages cleanly
 
-windows-reactor calls `MddBootstrapInitialize2` with `OnPackageIdentity_NOOP`
-(`crates/libs/reactor/src/app.rs`), so under MSIX **package identity** the App SDK bootstrapper is
-a no-op and the runtime is resolved from the manifest's `<PackageDependency>` on
-`Microsoft.WindowsAppRuntime.2` instead (reactor pins `WINDOWSAPPSDK_RELEASE_MAJORMINOR = 0x20000`
-= 2.0). It's a full-trust Win32 app (`EntryPoint="Windows.FullTrustApplication"` + `runFullTrust`)
-because it owns raw D3D11, Win32 low-level input hooks, WASAPI and SDL3.
+`main` calls `windows_reactor::bootstrap()`, which runs `MddBootstrapInitialize2` with
+`OnPackageIdentity_NOOP` (`crates/libs/reactor/src/bootstrap.rs`), so under MSIX **package
+identity** the App SDK bootstrapper is a no-op and the runtime is resolved from the manifest's
+`<PackageDependency>` on `Microsoft.WindowsAppRuntime.2` instead (reactor pins
+`WINDOWSAPPSDK_RELEASE_MAJORMINOR = 0x20000` = 2.0). It's a full-trust Win32 app
+(`EntryPoint="Windows.FullTrustApplication"` + `runFullTrust`) because it owns raw D3D11, Win32
+low-level input hooks, WASAPI and SDL3.
 
 ## Versioning