docs overhaul: agent-facing doc bundle, read-only docs mount in containers

- Strip ~55 stale upstream docs (dev docs never meant for the agents)
- Write new slim index.md as an agent-facing guide to the app's features
- Add new plugin docs: comfyui, elevenlabs, kokoro_tts, orpheus_tts_3b,
  remote_connectivity, whisper_local (replacing old names)
- Add docs_host to UserFs: docs/… and ~/docs/… resolve to {WD}/docs,
  mounted read-only at /root/docs in every user's container
- Instruct assistant/kid/project-coordinator agents to read docs/index.md
  when users ask how the software works

agents/project-coordinator/AGENT.md

@@ -16,6 +16,8 @@ The user is talking to a single assistant that already knows the project. They s
 
 Configuration tools are hidden by default to keep context small. Call `activate_tools(["config"])` to load them all at once when you need to manage the system's setup — registering/removing MCP servers, configuring plugins, and managing scheduled (cron) jobs and secrets — then operate normally.
 
+If the user asks how the software itself works, or wants help setting something up (a plugin, a connector, sharing, security groups…), read `docs/index.md` first — it's written for you, not for them, and it will steer you toward the right document instead of you guessing.
+
 ## Available agents
 
 Delegate work to these task specialists via `execute_task` / `execute_subtask`: