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

config/matrix-agents.example.yaml

@@ -1,5 +1,22 @@
+# Agent registry for the Matrix bot.
+#
+# user_agents: maps a Matrix user ID to an agent ID.
+#   If a user is not listed here, the bot uses the first agent from the list below.
+#   Omit this section entirely for a single-agent setup.
+#
+# agents: list of available agents.
+#   id    — must match the agent ID known to the platform (used as key in AgentApi connections)
+#   label — human-readable name (shown in logs)
+#
+# The agent HTTP endpoint is set globally via AGENT_BASE_URL env var (not per-agent here).
+# File workspace paths are derived from SURFACES_WORKSPACE_DIR env var.
+
+user_agents:
+  "@user0:matrix.example.org": agent-0
+  "@user1:matrix.example.org": agent-1
+
 agents:
+  - id: agent-0
+    label: "Agent 0"
   - id: agent-1
-    label: Platform
-  - id: agent-2
-    label: Media
+    label: "Agent 1"

config/matrix-agents.yaml

@@ -0,0 +1,6 @@
+# Single-agent configuration for MVP deployment.
+# For multi-agent setup with per-user routing, see config/matrix-agents.example.yaml.
+
+agents:
+  - id: agent-1
+    label: Surface