Simplify tray: static template icon, click focuses the app

The setImage-swapped progress frames lost the template treatment on macOS and
rendered black-on-dark once transfers started. Dial back per user decision:
the tray is now just the glyph (template image set once at construction, never
swapped) and clicking it activates the window — no menu, no progress effects.
Removes everything that only served the fancy version: progress frames +
generation, engine.aggregateProgress, the workspacesSync webview->bun channel
(schema, send proxy, panels effect, handlers) and the activate-tab action.

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

src/bun/transfers/engine.ts

@@ -146,35 +146,6 @@ 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()) {