Tray icon with live transfer progress and tabs menu

- AppTray: template menu-bar icon (22pt, adapts to light/dark). While
  transfers run it swaps to pre-rendered frames — faded arrows + a fill bar
  showing aggregate doneBytes/totalBytes of the queue (nearest 5%, throttled
  500ms); back to the glyph when idle. No runtime image encoding.
- Menu: one entry per tab (checkmark on the active one) with live per-tab
  transfer count and percentage (jobs mapped via session ids), an overall
  progress row while transferring, Show <app>, Quit. Selecting a tab
  activates the window and switches to it.
- First use of webview->bun messages: PanelsService pushes workspacesSync
  (tab names, sessions, active id) via a new ready-gated send proxy; verified
  end-to-end in the running app.
- engine.aggregateProgress(): totals + per-session breakdown over non-terminal
  jobs (unit-verified idle/mid-transfer/idle).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/shared/rpc.ts

@@ -15,7 +15,13 @@ import type {
 // pulling in bun-only type modules.
 //
 // bun.requests    = calls the webview makes, handled in src/bun/rpc-handlers.ts
+// bun.messages    = fire-and-forget pushes from the webview (tray state)
 // webview.messages = push events from bun, handled in ui rpc.service.ts
+
+export interface WorkspaceSyncInfo {
+	workspaces: { id: number; name: string; remote: boolean; sessionIds: string[] }[];
+	activeId: number;
+}
 export type AppRPC = {
 	bun: {
 		requests: {
@@ -97,7 +103,9 @@ export type AppRPC = {
 			};
 			clearEditLeftovers: { params: Record<string, never>; response: Result };
 		};
-		messages: Record<never, never>;
+		messages: {
+			workspacesSync: WorkspaceSyncInfo;
+		};
 	};
 	webview: {
 		requests: Record<never, never>;