feat: Matrix AI voice agent (LiveKit + LiteLLM)

Bot @ai:agiliton.eu accepts room invites, dispatches LiveKit agent.
Agent joins call with STT (Groq Whisper) → LLM (Sonnet) → TTS (ElevenLabs)
pipeline, all routed through LiteLLM.

CF-1147

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

agent.py

@@ -0,0 +1,58 @@
+import os
+import logging
+
+from livekit.agents import Agent, AgentSession, AgentServer, JobContext, JobProcess, cli
+from livekit.plugins import openai as lk_openai, elevenlabs, silero
+
+logger = logging.getLogger("matrix-ai-agent")
+
+LITELLM_URL = os.environ["LITELLM_BASE_URL"]
+LITELLM_KEY = os.environ.get("LITELLM_API_KEY", "not-needed")
+
+SYSTEM_PROMPT = """You are a helpful voice assistant in a Matrix call.
+Rules:
+- Keep answers SHORT — 1-3 sentences max
+- Be direct, no filler words
+- If the user wants more detail, they will ask
+- Speak naturally as in a conversation"""
+
+server = AgentServer()
+
+
+def prewarm(proc: JobProcess):
+    proc.userdata["vad"] = silero.VAD.load()
+
+
+server.setup_fnc = prewarm
+
+
+@server.rtc_session(agent_name="matrix-ai")
+async def entrypoint(ctx: JobContext):
+    model = os.environ.get("LITELLM_MODEL", "claude-sonnet")
+    voice_id = os.environ.get("ELEVENLABS_VOICE_ID", "21m00Tcm4TlvDq8ikWAM")
+
+    session = AgentSession(
+        stt=lk_openai.STT(
+            base_url=LITELLM_URL,
+            api_key=LITELLM_KEY,
+            model="whisper",
+        ),
+        llm=lk_openai.LLM(
+            base_url=LITELLM_URL,
+            api_key=LITELLM_KEY,
+            model=model,
+        ),
+        tts=elevenlabs.TTS(
+            voice=voice_id,
+            model="eleven_multilingual_v2",
+        ),
+        vad=ctx.proc.userdata["vad"],
+    )
+
+    agent = Agent(instructions=SYSTEM_PROMPT)
+    await session.start(agent=agent, room=ctx.room)
+    await session.generate_reply(instructions="Greet the user briefly.")
+
+
+if __name__ == "__main__":
+    cli.run_app(server)