feat: sovereign voice loop — timmy voice command

Adds fully local listen-think-speak voice interface.
STT: Whisper, LLM: Ollama, TTS: Piper. No cloud, no network.

- src/timmy/voice_loop.py: VoiceLoop with VAD, Whisper, Piper
- src/timmy/cli.py: new voice command
- pyproject.toml: voice extras updated
- 20 new tests

pyproject.toml

@@ -43,6 +43,9 @@ python-telegram-bot = { version = ">=21.0", optional = true }
 "discord.py" = { version = ">=2.3.0", optional = true }
 airllm = { version = ">=2.9.0", optional = true }
 pyttsx3 = { version = ">=2.90", optional = true }
+openai-whisper = { version = ">=20231117", optional = true }
+piper-tts = { version = ">=1.2.0", optional = true }
+sounddevice = { version = ">=0.4.6", optional = true }
 sentence-transformers = { version = ">=2.0.0", optional = true }
 numpy = { version = ">=1.24.0", optional = true }
 requests = { version = ">=2.31.0", optional = true }
@@ -59,7 +62,7 @@ pytest-xdist = { version = ">=3.5.0", optional = true }
 telegram = ["python-telegram-bot"]
 discord = ["discord.py"]
 bigbrain = ["airllm"]
-voice = ["pyttsx3"]
+voice = ["pyttsx3", "openai-whisper", "piper-tts", "sounddevice"]
 celery = ["celery"]
 embeddings = ["sentence-transformers", "numpy"]
 git = ["GitPython"]