feat(deploy): platform handoff — agent routing, persistence, docs cleanup

Agent routing:
- Remove !agent command and manual agent selection flow
- Registry auto-assigns agent from user_agents mapping (fallback: agents[0])
- provision_workspace_chat and !new both write agent_id to room_meta
- Reconciliation backfills agent_id from registry on cold start
- Fix duplicate agent_id block in auth.py

Deployment stability:
- Add bot-state named volume to persist lambda_matrix.db and matrix_store
- Fix docker-compose.prod.yml duplicate environment: key (was silently losing all Matrix credentials)
- Fix MATRIX_AGENT_REGISTRY_PATH to use absolute container path /app/config/...
- Add bot-state volume declaration to docker-compose.fullstack.yml

Docs and config:
- Rewrite README.md for platform handoff (deploy table, working commands only)
- Rewrite docs/matrix-prototype.md (remove stale commands and mock descriptions)
- Remove !save/!load/!context/!agent from help text and welcome message
- Add !clear, !list, !remove, !yes/!no to help text
- Clean up .env.example (remove Telegram token, internal vars, real URLs)
- Update config/matrix-agents.example.yaml with user_agents section and comments
- Add explanatory comment to Dockerfile for --ignore-requires-python
- Remove silent uv sync fallbacks in Dockerfile

adapter/matrix/reconciliation.py

@@ -125,6 +125,15 @@ async def reconcile_startup_state(client: object, runtime: object) -> Reconcilia
             room_meta["platform_chat_id"] = await next_platform_chat_id(runtime.store)
             result.backfilled_platform_chat_ids += 1
 
+        if not room_meta.get("agent_id"):
+            registry = getattr(runtime, "registry", None)
+            if registry is not None:
+                agent_id = registry.get_agent_id_for_user(matrix_user_id)
+                if agent_id is None and registry.agents:
+                    agent_id = registry.agents[0].agent_id
+                if agent_id:
+                    room_meta["agent_id"] = agent_id
+
         if existing_meta is None:
             result.recovered_rooms += 1
         elif room_meta != existing_meta: