test(companion): add platform waitForIdle integration coverage

docs/plans/state.json

@@ -916,6 +916,17 @@
       ],
       "test_status": "pnpm test:run src/companion/runtimeClient.test.ts src/companion/platformClients.test.ts src/companion/heartbeatLoop.test.ts src/companion/platformClients.integration.test.ts + pnpm typecheck passing"
     },
+    "companion-platform-wait-for-idle-integration-coverage": {
+      "status": "completed",
+      "date": "2026-02-17",
+      "updated": "2026-02-17",
+      "summary": "Added platform integration coverage for `waitForIdle()` to verify idle-drain synchronization resolves after pending event waiters are cleared via platform wrapper APIs.",
+      "files_modified": [
+        "src/companion/platformClients.integration.test.ts",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/companion/platformClients.integration.test.ts src/companion/platformClients.test.ts src/companion/runtimeClient.test.ts src/companion/heartbeatLoop.test.ts + pnpm typecheck passing"
+    },
     "browser-tools-activation-clarity": {
       "status": "completed",
       "date": "2026-02-17",

src/companion/platformClients.integration.test.ts

@@ -150,6 +150,27 @@ describe('platform clients integration', () => {
     expect(client.pendingEventWaitCount).toBe(0);
   });
 
+  it('platform waitForIdle resolves after pending waiters are cleared', async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+
+    const runtime = createRuntime();
+    const client = new IOSCompanionClient({ runtime, nodeId: 'ios-wait-idle-e2e' });
+
+    const pending = client.waitForAnyEvent(['agent.stream'], { timeoutMs: 10_000 }).catch(() => undefined);
+    expect(client.hasPendingWork).toBe(true);
+
+    const idle = client.waitForIdle({ timeoutMs: 1_000, pollIntervalMs: 5 });
+    setTimeout(() => {
+      client.clearEventSubscriptions();
+    }, 20);
+
+    await expect(idle).resolves.toBeUndefined();
+    await pending;
+    expect(client.hasPendingWork).toBe(false);
+  });
+
   it('platform connected reflects runtime connection lifecycle', async () => {
     if (!LISTEN_ALLOWED) {
       return;