feat(desktop): per-session metadata and status icons in the tray menu

Enrich each session row in the macOS tray menu and refine its layout.

- Add a "project · branch" sublabel to every session row, resolved from the
  session directory: project-root sessions map to their project + live/cached
  git branch; worktree sessions map back to their parent project and use the
  worktree's branch. Branch resolution falls back live VCS → git store → worktree
  metadata, with normalized directory keys.
- Replace the inline text status glyph with a native left-aligned status icon
  (vertically centred across the title + sublabel). Idle rows use a transparent
  placeholder so every row shares the same gutter and both text lines align.
- Status icons use the app icon set: pulse (busy), check (unread), error-warning
  (error), loop-right (retry); all rendered as tinted template images.
- Drop the unread count "(n)" from the row label — the check icon already
  signals it and the number wasn't self-explanatory.
- Show the first 8 sessions inline; the rest stay in the overflow submenu.
- Subscribe the tray to the projects, worktree and git stores so subtitles stay
  current.

packages/electron/main.mjs

@@ -4080,11 +4080,21 @@ const resolveTraySurface = () => {
 
 const trayIconAssets = () => {
   const dir = path.join(resourceRoot(), 'icons', 'tray');
+  const statusDir = path.join(dir, 'status');
   return {
     idleIconPath: path.join(dir, 'trayTemplate-idle.png'),
     unseenIconPath: path.join(dir, 'trayTemplate-unseen.png'),
     breathIconPaths: Array.from({ length: TRAY_BREATH_FRAME_COUNT }, (_, i) =>
       path.join(dir, `trayTemplate-breath-${String(i).padStart(2, '0')}.png`)),
+    // Per-session status icons shown in the menu rows (left, vertically centred
+    // across the title + sublabel). 'blank' reserves the gutter for idle rows.
+    statusIconPaths: {
+      busy: path.join(statusDir, 'busy.png'),
+      retry: path.join(statusDir, 'retry.png'),
+      error: path.join(statusDir, 'error.png'),
+      unseen: path.join(statusDir, 'unseen.png'),
+      blank: path.join(statusDir, 'blank.png'),
+    },
   };
 };