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/bun/transfers/engine.ts

@@ -146,6 +146,35 @@ export class TransferEngine {
 		if (job && TERMINAL.includes(job.snapshot.state)) this.jobs.delete(jobId);
 	}
 
+	/** Live totals over every non-terminal job (drives the tray progress icon). */
+	aggregateProgress(): {
+		activeCount: number;
+		doneBytes: number;
+		totalBytes: number;
+		bySession: Record<string, { count: number; done: number; total: number }>;
+	} {
+		const result = {
+			activeCount: 0,
+			doneBytes: 0,
+			totalBytes: 0,
+			bySession: {} as Record<string, { count: number; done: number; total: number }>,
+		};
+		for (const job of this.jobs.values()) {
+			const snap = job.snapshot;
+			if (TERMINAL.includes(snap.state)) continue;
+			result.activeCount++;
+			result.doneBytes += snap.doneBytes;
+			result.totalBytes += snap.totalBytes;
+			for (const sessionId of new Set([snap.srcSessionId, snap.dstSessionId])) {
+				const entry = (result.bySession[sessionId] ??= { count: 0, done: 0, total: 0 });
+				entry.count++;
+				entry.done += snap.doneBytes;
+				entry.total += snap.totalBytes;
+			}
+		}
+		return result;
+	}
+
 	/** Fail every non-terminal job that touches a dead session. */
 	failSession(sessionId: string, reason: string): void {
 		for (const job of this.jobs.values()) {