feat(companion): add cancellable pending event wait helper

src/companion/runtimeClient.test.ts

@@ -389,6 +389,29 @@ describe('CompanionRuntimeClient', () => {
     await awaited;
   });
 
+  it('cancelPendingEventWaits rejects waiters without clearing subscriptions', async () => {
+    const client = new CompanionRuntimeClient({
+      url: 'ws://127.0.0.1:1',
+    });
+    const handler = vi.fn();
+    client.subscribeEvents(handler);
+
+    const awaited = expect(
+      client.waitForEvent('agent.stream', { timeoutMs: 10_000 }),
+    ).rejects.toThrow('manually cancelled');
+    client.cancelPendingEventWaits('manually cancelled');
+    await awaited;
+
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 99,
+        event: 'agent.stream',
+        data: { token: 'still-subscribed' },
+      }),
+    );
+    expect(handler).toHaveBeenCalledWith('agent.stream', { token: 'still-subscribed' });
+  });
+
   it('waitForEvent rejects immediately on disconnect', async () => {
     const client = new CompanionRuntimeClient({
       url: 'ws://127.0.0.1:1',