Fix idle pause during LISTEN audio gaps (followup to #2893)

frontend/app/services/audio.ts

@@ -34,6 +34,7 @@ import type { Signal as SignalModel } from 'brn/schemas/signal';
 import Intl from 'ember-intl/services/intl';
 import { PolySynth, Synth, SynthOptions } from 'tone';
 import UserDataService from './user-data';
+import StudyingTimerService from './studying-timer';
 import type { Exercise } from 'brn/schemas/exercise';
 
 type ISourceCollection = (ISource | IToneSource | null)[];
@@ -52,6 +53,7 @@ export default class AudioService extends Service {
   @service('stats') declare stats: StatsService;
   @service('intl') declare intl: Intl;
   @service('user-data') declare userData: UserDataService;
+  @service('studying-timer') declare studyingTimer: StudyingTimerService;
   context!: AudioContext;
 
   willDestroy(): void {
@@ -218,6 +220,7 @@ export default class AudioService extends Service {
 
   @action
   async playAudio() {
+    this.studyingTimer.resetIdle();
     try {
       if (!isTesting()) {
         await this.playTask.perform();

frontend/app/services/studying-timer.ts

@@ -66,14 +66,28 @@ export default class StudyingTimerService extends Service {
   }
   @action
   maybeIdlePause() {
-    // Pause cascades into audio.stop() via task-player.onPauseStateChanged,
-    // which would interrupt exercises whenever the user stops moving the mouse.
+    // resetIdle() (invoked on every playAudio) is the primary mechanism that
+    // keeps the watcher from firing mid-sequence. This guard is a defensive
+    // backstop in case a single clip ever outruns the idle window: pause
+    // cascades into audio.stop() via task-player.onPauseStateChanged, which
+    // would interrupt exercises whenever the user stops moving the mouse.
     if (this.audio.isPlaying) {
       return;
     }
     this.pause();
   }
   @action
+  resetIdle() {
+    if (this.idleWatcher) {
+      try {
+        this.idleWatcher.stop();
+        this.idleWatcher.start();
+      } catch (_e) {
+        // idle-js may not support stop/start cycle in some edge cases
+      }
+    }
+  }
+  @action
   async startIdleWatcher() {
     if (isTesting()) {
       return;

frontend/tests/unit/services/studying-timer-test.js

@@ -36,4 +36,43 @@ module('Unit | Service | studying-timer', function (hooks) {
       assert.true(timer.isPaused);
     });
   });
+
+  module('resetIdle', function () {
+    test('rearms the idle watcher via stop/start', function (assert) {
+      const timer = this.owner.lookup('service:studying-timer');
+      let stopCount = 0;
+      let startCount = 0;
+      timer.idleWatcher = {
+        stop() {
+          stopCount++;
+        },
+        start() {
+          startCount++;
+        },
+      };
+      timer.resetIdle();
+      assert.strictEqual(stopCount, 1, 'idleWatcher.stop called once');
+      assert.strictEqual(startCount, 1, 'idleWatcher.start called once');
+    });
+
+    test('does not toggle isPaused', function (assert) {
+      // Regression guard: resetIdle must not clear a user-initiated pause.
+      const timer = this.owner.lookup('service:studying-timer');
+      timer.idleWatcher = { stop() {}, start() {} };
+      timer.pause();
+      timer.resetIdle();
+      assert.true(timer.isPaused, 'user pause remains sticky after resetIdle');
+    });
+
+    test('is a no-op when idleWatcher is null', function (assert) {
+      const timer = this.owner.lookup('service:studying-timer');
+      timer.idleWatcher = null;
+      try {
+        timer.resetIdle();
+        assert.ok(true, 'did not throw');
+      } catch (_e) {
+        assert.ok(false, 'resetIdle threw with null idleWatcher');
+      }
+    });
+  });
 });