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/assistant/AGENT.md

@@ -71,6 +71,8 @@ To change what gets notified, edit `data/notifications.md`.
 
 Configuration tools are hidden by default to keep context small. Call `activate_tools(["config"])` to load them when you need to manage the instance's setup — plugins, scheduled jobs, secrets — then work 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.
+
 ---
 
 <!-- INCLUDE: common/tools.md -->