fix(audio): gate the executor's chain-plan startAudio behind the user-stop latch

Second field finding: a user-stopped engine came back when a song load
ran a rig_builder chain plan with startAudio:true - the executor calls
native startAudio directly in the main process, bypassing the IPC latch
check entirely (plan 6.1's second writer).

Decision (strict 8.3): only the device screen's user start resumes.
lease-bridge gains gateNativeAudio(), a proxy over the native accessor
that suppresses startAudio while latched (log-once telemetry line);
audio-bridge hands the executor the gated accessor.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/lease-bridge.test.js

@@ -127,6 +127,31 @@ test('user-stop latch: fresh demands and legacy starts held off until user start
     bridge.dispose();
 });
 
+test('gateNativeAudio: executor startAudio suppressed under the latch, transparent otherwise', () => {
+    const audio = fakeAudio();
+    const { bridge } = makeBridge(audio);
+    const gated = bridge.gateNativeAudio(() => audio)();
+
+    // Transparent pass-through when not latched — other methods untouched.
+    gated.startAudio();
+    assert.deepEqual(audio.calls, ['start']);
+    assert.equal(gated.isAudioRunning(), true);
+
+    audio.stopAudio();
+    audio.calls.length = 0;
+    bridge.onUserStopAudio();
+
+    // Chain plan's startAudio:true waits out the user stop (strict §8.3).
+    gated.startAudio();
+    assert.deepEqual(audio.calls, []);
+
+    bridge.onUserStartAudio(); // user start clears; engine started by it
+    audio.calls.length = 0;
+    gated.startAudio();
+    assert.deepEqual(audio.calls, ['start']);
+    bridge.dispose();
+});
+
 test('detection demand arms native; raw disarm guarded while demand active (6.3)', () => {
     const audio = fakeAudio();
     const { bridge } = makeBridge(audio);