feat(clients): windows shortcut parity (Ctrl+Alt+Shift+S, F11) + surface stream shortcuts

Windows was missing two of the four stream shortcuts the GTK client has:
Ctrl+Alt+Shift+S (toggle the stats overlay live) and F11 (toggle fullscreen).
Add both to the low-level keyboard hook — S flips a HUD_VISIBLE atomic seeded
from Settings::show_hud at install (Settings is the default, the key overrides
it for the session, matching GTK), F11 drives a borderless-fullscreen toggle on
the window HWND and re-locks the pointer geometry for the new client rect. Both
are consumed locally, never sent on the wire.

Surface the full key set in two places, on both clients:
- in the UI: a read-only "In-stream keyboard shortcuts" reference card in the
  Windows Settings > Input section (the counterpart of the GTK Shortcuts
  window), plus the expanded HUD hint; the Linux keyboard hint gains F11.
- at stream start: a bottom-centre banner listing the shortcuts for the first
  few seconds of every session, independent of the HUD setting. Linux gets the
  matching start-flash of its capture hint (capture engages on map and hid it,
  so the keys were never shown until the first release).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/windows/src/app/settings.rs

@@ -109,6 +109,59 @@ fn settings_card(controls: Vec<Element>) -> Element {
     card(vstack(controls).spacing(10.0)).into()
 }
 
+/// The in-stream keyboard shortcuts, in the GTK Shortcuts window's order: the chord, then what it
+/// does. Read-only — the bindings themselves live in the input hook (`crate::input`); this is the
+/// Windows analogue of that window, so both clients document the same set.
+const STREAM_SHORTCUTS: &[(&str, &str)] = &[
+    ("F11", "Toggle fullscreen"),
+    (
+        "Ctrl+Alt+Shift+Q",
+        "Release captured input (click the stream to recapture)",
+    ),
+    ("Ctrl+Alt+Shift+D", "Disconnect"),
+    ("Ctrl+Alt+Shift+S", "Toggle the statistics overlay"),
+];
+
+/// A subtle key-cap chip for the shortcuts reference — the chord on a filled, bordered pill.
+fn key_chip(keys: &str) -> Element {
+    border(text_block(keys).font_size(12.0).semibold())
+        .background(ThemeRef::SubtleFill)
+        .border_brush(ThemeRef::CardStroke)
+        .border_thickness(uniform(1.0))
+        .corner_radius(6.0)
+        .padding(edges(8.0, 3.0, 8.0, 3.0))
+        .horizontal_alignment(HorizontalAlignment::Left)
+        .into()
+}
+
+/// A read-only reference card listing the in-stream keyboard shortcuts — the Windows counterpart of
+/// the GTK client's Keyboard Shortcuts window. One grid, chord chip then action, so the actions
+/// line up across rows.
+fn shortcuts_reference() -> Element {
+    let mut children: Vec<Element> = Vec::new();
+    for (i, (keys, action)) in STREAM_SHORTCUTS.iter().enumerate() {
+        let row = i as i32;
+        children.push(key_chip(keys).grid_row(row).grid_column(0));
+        let action_cell: Element = text_block(*action)
+            .foreground(ThemeRef::SecondaryText)
+            .vertical_alignment(VerticalAlignment::Center)
+            .into();
+        children.push(action_cell.grid_row(row).grid_column(1));
+    }
+    let table = grid(children)
+        .columns([GridLength::Auto, GridLength::Star(1.0)])
+        .rows(vec![GridLength::Auto; STREAM_SHORTCUTS.len()])
+        .column_spacing(12.0)
+        .row_spacing(6.0);
+    card(vstack((
+        text_block("In-stream keyboard shortcuts")
+            .semibold()
+            .margin(edges(0.0, 0.0, 0.0, 8.0)),
+        table,
+    )))
+    .into()
+}
+
 /// The settings screen: a stock WinUI `NavigationView` (the Windows-Settings sidebar pattern) —
 /// one pane item per section, the section's card as the content, the built-in back arrow
 /// returning to the host list. `section`/`set_section` are the selected pane tag, held in ROOT
@@ -315,7 +368,10 @@ pub(crate) fn settings_page(
     let hud_toggle = setting_toggle(ctx, "Show the stats overlay (HUD)", s.show_hud, |s, on| {
         s.show_hud = on
     })
-    .tooltip("The in-stream overlay: mode, codec, fps, bitrate, latency, decode path.");
+    .tooltip(
+        "The in-stream overlay: mode, codec, fps, bitrate, latency, decode path. \
+         Ctrl+Alt+Shift+S toggles it live while streaming.",
+    );
 
     let licenses_button = {
         let ss = set_screen.clone();
@@ -343,11 +399,16 @@ pub(crate) fn settings_page(
         ),
         "input" => (
             "Input",
-            settings_card(vec![
-                forward_combo.into(),
-                pad_combo.into(),
-                shortcuts_toggle.into(),
-            ]),
+            vstack((
+                settings_card(vec![
+                    forward_combo.into(),
+                    pad_combo.into(),
+                    shortcuts_toggle.into(),
+                ]),
+                shortcuts_reference(),
+            ))
+            .spacing(14.0)
+            .into(),
         ),
         "audio" => (
             "Audio",