feat(chat): add voice playback with auto-play and visual effects (#396)
## Features
### Core Functionality
- **Web Speech API Integration**: Add TTS (text-to-speech) playback for assistant messages
- **Manual Playback**: Click-to-play button next to each assistant message (🔊 icon)
- **Auto-play Mode**: Toggle switch in input bar to auto-play responses
- **Playback Controls**: Play/pause/stop with visual feedback
### User Interface
- **Playback Button**: Hover-activated button in message meta area (next to copy button)
- **Auto-play Switch**: Voice icon toggle in input top bar with state persistence
- **Mobile Optimization**: Buttons always visible on mobile (≤768px width)
- **Visual Feedback**:
- Rainbow glowing border during playback (2px border, 10px/20px glow)
- 4-second animation cycle through 6 colors
- Play/pause icon toggle
### Voice Customization
- **Pitch/Rate Control**: Low-pitched (0.5) fast-speaking (1.2) "male voice"
- **Auto Voice Selection**: Attempts to select male voices across platforms (macOS: Yaoyao, Windows: David/Daniel)
- **Platform Compatibility**: Works with system-provided voices on macOS, iOS, Android, Windows
### Content Filtering
- Smart text extraction: filters code blocks, `<thinking>` tags, HTML
- Only assistant messages are eligible for playback
- Tool and system messages are excluded
### Internationalization
- Added 8 language translations (en, zh, de, es, fr, ja, ko, pt)
- New keys: `playSpeech`, `pauseSpeech`, `resumeSpeech`, `stopSpeech`, `autoPlaySpeech`, `speechNotSupported`
## Technical Details
### New Files
- `packages/client/src/composables/useSpeech.ts`: Core speech synthesis composable
- Voice loading and selection logic
- Single-instance global speech manager
- Event handling (onstart, onend, onerror, onboundary)
- State management (isPlaying, isPaused, currentMessageId)
### Modified Components
- **ChatInput.vue**: Auto-play switch with localStorage persistence
- **MessageItem.vue**:
- Playback button integration
- Event listener for auto-play triggers
- Mobile-first button visibility
- Rainbow border animation during playback
### Store Changes
- `chat.ts`:
- Added `autoPlaySpeechEnabled` state
- `setAutoPlaySpeech()` method
- `playMessageSpeech()` method for event-based playback
- Auto-play trigger on `run.completed` event
## Browser Support
- Requires Web Speech API support (all modern browsers)
- Graceful degradation: button hidden if API not supported
- Voice availability varies by platform and OS
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
