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/Cargo.toml

@@ -25,11 +25,11 @@ punktfunk-core = { path = "../../crates/punktfunk-core", features = ["quic"] }
 # `build.rs` downloads the Windows App SDK NuGets and stages the bootstrap DLL + resources.pri
 # next to the exe; it requires `CARGO_WORKSPACE_DIR` to be set in the build env. Unpublished
 # (version 0.0.0) and fast-moving, so pinned to a verified commit.
-windows-reactor = { git = "https://github.com/microsoft/windows-rs", rev = "b4129fcc1ae81eec8bf1217539883db821bca3a1" }
+windows-reactor = { git = "https://github.com/microsoft/windows-rs", rev = "a4f7b2cb7c63c6bb7fc77a2affe57145be1d8c4f" }
 # Win32 / Direct3D11 / DXGI for the SwapChainPanel composition swapchain. Pulled from the SAME
 # windows-rs commit as windows-reactor so their `windows-core` unifies — the `IDXGISwapChain1`
 # we hand to `SwapChainPanelHandle::set_swap_chain` must satisfy reactor's `windows_core::Interface`.
-windows = { git = "https://github.com/microsoft/windows-rs", rev = "b4129fcc1ae81eec8bf1217539883db821bca3a1", features = [
+windows = { git = "https://github.com/microsoft/windows-rs", rev = "a4f7b2cb7c63c6bb7fc77a2affe57145be1d8c4f", features = [
     "Win32_Foundation",
     "Win32_Graphics_Dxgi",
     "Win32_Graphics_Dxgi_Common",
@@ -69,5 +69,8 @@ tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 
 # Embeds the app icon as an exe resource (build.rs) — Windows hosts only (rc.exe from the SDK).
+# windows-reactor-setup stages the Windows App SDK runtime bootstrap (framework-dependent) next
+# to the exe — the new-model replacement for the old windows-reactor build.rs; same pinned rev.
 [target.'cfg(windows)'.build-dependencies]
 winresource = "0.1"
+windows-reactor-setup = { git = "https://github.com/microsoft/windows-rs", rev = "a4f7b2cb7c63c6bb7fc77a2affe57145be1d8c4f" }