fix(browse): 'browse stop' no longer restarts the daemon it was asked to stop

The stop handler awaited shutdown() — which ends in process.exit — before
returning, so the acknowledgement never egressed. The CLI's fetch reset,
which its crash path reasonably interpreted as a dead daemon: it relaunched
Chromium, re-sent stop, watched the daemon exit again, and errored 'Server
crashed twice in a row'. Every stop cost a wasted Chromium launch and a
nonzero exit. The ack now returns first; shutdown fires on a 25ms unref'd
timer. Same fix for restart. Fork's test pins ack-before-teardown for both.

Ported from time-attack/gstack (GStack 2).

Co-authored-by: Sina Matian <sina@time-attack.dev>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

browse/test/stop-ack-before-shutdown.test.ts

@@ -0,0 +1,23 @@
+import { describe, expect, test } from 'bun:test';
+import { handleMetaCommand } from '../src/meta-commands';
+
+describe('server control acknowledgement ordering', () => {
+  for (const [command, acknowledgement] of [
+    ['stop', 'Server stopped'],
+    ['restart', 'Restarting...'],
+  ] as const) {
+    test(`${command} acknowledges before closing the listener`, async () => {
+      let shutdownCalls = 0;
+      const manager = { getActiveSession: () => ({}) } as any;
+
+      const result = await handleMetaCommand(command, [], manager, async () => {
+        shutdownCalls += 1;
+      });
+
+      expect(result).toBe(acknowledgement);
+      expect(shutdownCalls).toBe(0);
+      await new Promise((resolve) => setTimeout(resolve, 50));
+      expect(shutdownCalls).toBe(1);
+    });
+  }
+});