fix(pi): keep active runs alive during background sleep

tests/unit/background-lifecycle.test.ts

@@ -50,6 +50,36 @@ describe('BackgroundLifecycleController', () => {
     controller.dispose();
   });
 
+  it('does not stop the runtime when a lease is acquired while sleep preparation is in flight', async () => {
+    vi.useFakeTimers();
+    let finishSleepPreparation!: () => void;
+    const sleepPreparation = new Promise<void>((resolve) => {
+      finishSleepPreparation = resolve;
+    });
+    const onSleep = vi.fn(() => sleepPreparation);
+    const onStopRuntime = vi.fn().mockResolvedValue(undefined);
+    const controller = new BackgroundLifecycleController({
+      idleStopMs: 60_000,
+      onSleep,
+      onStopRuntime,
+    });
+
+    controller.setActivity({ visible: false, module: 'learning' });
+    await vi.advanceTimersByTimeAsync(60_000);
+    expect(onSleep).toHaveBeenCalledTimes(1);
+
+    const release = controller.acquireLease({ id: 'coding-run:1', kind: 'coding-run' });
+    finishSleepPreparation();
+    await vi.runAllTicks();
+
+    expect(onStopRuntime).not.toHaveBeenCalled();
+
+    release();
+    await vi.advanceTimersByTimeAsync(60_000);
+    expect(onStopRuntime).toHaveBeenCalledTimes(1);
+    controller.dispose();
+  });
+
   it('cancels the idle stop when programming becomes visible again', async () => {
     vi.useFakeTimers();
     const onSleep = vi.fn();