Add fallback-tier TTS provider using Piper via OpenedAI Speech for
ultra-lightweight CPU-only synthesis. Maps 6 standard OpenAI voice
names (alloy, echo, fable, onyx, nova, shimmer) to Piper voices.
Update factory to use the new PiperTtsProvider class, replacing the
inline stub. Includes 37 unit tests covering provider identity,
voice mapping, and voice listing.
Fixes#395
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Extract KokoroTtsProvider from factory into its own module with:
- Full voice catalog of 54 built-in voices across 8 languages
- Voice metadata parsing from ID prefix (language, gender, accent)
- Exported constants for supported formats and speed range
- Comprehensive unit tests (48 tests)
- Fix lint/type errors in chatterbox provider (Prettier + unsafe cast)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add the BaseTTSProvider abstract class and TTS provider factory that were
part of the tiered TTS architecture but missed from the previous commit.
- BaseTTSProvider: abstract base with synthesize(), listVoices(), isHealthy()
- tts-provider.factory: creates Kokoro/Chatterbox/Piper providers from config
- 30 tests (22 base provider + 8 factory)
Refs #391
