feat(desktop): Tier A desktop features — web side (P5-46/36/44/43/49/47/55/57)

Web half of the desktop feature wave. A shared bridge (`hooks/useTauri.ts`:
invokeTauri/isTauri/useTauriEvent) backs per-feature hooks that no-op in the
browser and drive the native Tauri commands (compiled in cinny-desktop):

- P5-46 useTauriCallPower — hold system awake while a call is active.
- P5-36 useTauriJumpList — Windows jump list of recent rooms → matrix: deep links.
- P5-44 useTauriThumbbar — taskbar Mute/Deafen/End; events toggle mic/sound/hangup.
- P5-43 useTauriSmtc — SMTC call state + button events.
- P5-49 useTauriNetwork — react to native network-change → mx.retryImmediately().
- P5-47 window chrome — opt-in `customWindowChromeAtom` + TDS `TitleBar`; DesktopChrome
  wrapper in App.tsx (zero layout impact when off) + a desktop-only settings toggle.
- P5-55 composer toolbar drag-reorder (settings order[] + pragmatic-drag-and-drop).
- P5-57 DraftIndicator — subtle "draft saved" cue in the composer.

Client-scoped hooks mount via TauriDesktopFeatures in ClientNonUIFeatures; window
chrome mounts at App level. Gates: tsc/eslint/prettier clean, build OK, 556 tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/desktop/TitleBar.css.ts

@@ -0,0 +1,77 @@
+import { style } from '@vanilla-extract/css';
+import { DefaultReset, color, config, toRem } from 'folds';
+
+const BAR_HEIGHT = toRem(32);
+const CONTROL_WIDTH = toRem(46);
+
+export const TitleBar = style([
+  DefaultReset,
+  {
+    display: 'flex',
+    alignItems: 'stretch',
+    flexShrink: 0,
+    height: BAR_HEIGHT,
+    width: '100%',
+    backgroundColor: color.SurfaceVariant.Container,
+    color: color.SurfaceVariant.OnContainer,
+    borderBottom: `${toRem(1)} solid ${color.SurfaceVariant.ContainerLine}`,
+    // Sit above app content but never intercept scroll etc. below the bar.
+    userSelect: 'none',
+  },
+]);
+
+// The draggable region carries `data-tauri-drag-region`; it must expand to fill
+// the free space so most of the bar is grabbable.
+export const DragRegion = style({
+  display: 'flex',
+  alignItems: 'center',
+  flexGrow: 1,
+  minWidth: 0,
+  gap: config.space.S200,
+  paddingInline: config.space.S300,
+});
+
+export const Brand = style({
+  display: 'flex',
+  alignItems: 'center',
+  gap: config.space.S200,
+  // Children shouldn't swallow the drag; the region itself owns the attribute.
+  pointerEvents: 'none',
+});
+
+export const Controls = style({
+  display: 'flex',
+  alignItems: 'stretch',
+  flexShrink: 0,
+});
+
+export const ControlButton = style([
+  DefaultReset,
+  {
+    display: 'flex',
+    alignItems: 'center',
+    justifyContent: 'center',
+    width: CONTROL_WIDTH,
+    height: '100%',
+    padding: 0,
+    border: 'none',
+    cursor: 'pointer',
+    backgroundColor: 'transparent',
+    color: 'inherit',
+    transition: 'background-color 100ms ease',
+    selectors: {
+      '&:hover': {
+        backgroundColor: color.SurfaceVariant.ContainerLine,
+      },
+    },
+  },
+]);
+
+export const ControlButtonClose = style({
+  selectors: {
+    '&:hover': {
+      backgroundColor: color.Critical.Main,
+      color: color.Critical.OnMain,
+    },
+  },
+});