fix(app-expo): allow read-aloud on other split segments while TTS paused

Match playback refs to the correct assistant segment so the interrupt overlay
does not block other bubbles, and preempt local playback when switching segments.

Co-authored-by: Cursor <cursoragent@cursor.com>

app-expo/tests/features/conversation/message-split.test.ts

@@ -2,6 +2,8 @@ import {
   assistantSegmentMessageId,
   lastSegmentPreview,
   normalizeAssistantContentForSplit,
+  parseAssistantSplitListKey,
+  playbackListKeyMatchesBubble,
   splitMessageParts,
   splitStreamingSegments,
 } from '@/features/conversation/message-split';
@@ -75,6 +77,28 @@ describe('message-split', () => {
     expect(assistantSegmentMessageId('uuid-a', 1)).toBe('uuid-a_seg_1');
   });
 
+  it('playbackListKeyMatchesBubble aligns seg playback with part listKey', () => {
+    const uuid = '78b32c06-d2f9-453b-9cc4-354e68fbcb2d';
+    expect(
+      playbackListKeyMatchesBubble(
+        `${uuid}_seg_1`,
+        `${uuid}_part_1`,
+        uuid,
+      ),
+    ).toBe(true);
+    expect(
+      playbackListKeyMatchesBubble(
+        `${uuid}_seg_0`,
+        `${uuid}_part_1`,
+        uuid,
+      ),
+    ).toBe(false);
+    expect(parseAssistantSplitListKey(`${uuid}_part_0`)).toEqual({
+      messageId: uuid,
+      segmentIndex: 0,
+    });
+  });
+
   it('normalizeAssistantContentForSplit maps fullwidth brackets', () => {
     expect(normalizeAssistantContentForSplit('［x］')).toBe('[x]');
     expect(normalizeAssistantContentForSplit('【x】')).toBe('[x]');