fix(#647): pin the hold timer's own re-render

The timer test only checked that a handle existed, and the other hold tests
re-rendered by hand, so deleting the re-render from the timer callback left
every test green. A new test waits out the hold for real and asserts the
suffix appears and the timer is spent with no further call.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/connection-indicator.test.ts

@@ -203,6 +203,19 @@ describe('connection indicator — a brief burst does not widen the pill', () =>
     app._updateConnectionIndicator(); // cancels it
   });
 
+  it('shows the count by itself once the hold elapses, and the timer is spent', async () => {
+    // A real wait, on purpose: the vm context runs on its own Date and the real setTimeout, so this
+    // exercises the shipped timer callback rather than a manual re-render.
+    const { app, els } = makeApp({ activeSessionId: 's1', _wsState: 'connected', queuedBytes: 40 });
+    app._updateConnectionIndicator();
+    expect(els.connectionText.textContent).toBe('WS');
+    await new Promise((r) => setTimeout(r, 1400));
+    expect(els.connectionText.textContent).toBe('WS · 40B queued');
+    expect((app as unknown as { _backlogHoldTimer: unknown })._backlogHoldTimer).toBeNull();
+    app._pendingDeliveries.clear();
+    app._updateConnectionIndicator();
+  });
+
   it('shows the count once the same backlog has stayed up past the hold', () => {
     const { app, els } = makeApp({ activeSessionId: 's1', _wsState: 'connected', queuedBytes: 40 });
     app._updateConnectionIndicator();