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/src/trust.rs

@@ -149,12 +149,19 @@ pub struct Settings {
     /// vanished adapter (eGPU unplugged) falls back to automatic.
     #[serde(default)]
     pub adapter: String,
+    /// Show the stats/info overlay (HUD) over the stream.
+    #[serde(default = "default_true")]
+    pub show_hud: bool,
 }
 
 fn default_codec() -> String {
     "auto".into()
 }
 
+fn default_true() -> bool {
+    true
+}
+
 impl Settings {
     /// The `codec` setting as a `quic::CODEC_*` preference bit (`0` = auto).
     pub fn preferred_codec(&self) -> u8 {
@@ -183,6 +190,7 @@ impl Default for Settings {
             decoder: "auto".into(),
             codec: "auto".into(),
             adapter: String::new(),
+            show_hud: true,
         }
     }
 }