Improve local agent chat and device health detection

README.md

@@ -80,6 +80,25 @@ uv run --package device-host-agent device-host-agent
 implements OpenAI `/chat/completions`. Hosted `openai` and `anthropic` providers
 also accept `AI_PLANNER_API_KEY` and their conventional API key variables.
 
+The local Host console also exposes an authenticated conversational Agent API:
+
+```text
+POST http://127.0.0.1:8765/api/chat
+```
+
+Send a JSON body containing `messages` (`user`/`assistant` roles). The Agent can
+return ordinary assistant text or call the same device-operation tool contracts
+used by the Runtime; each tool result is fed back to the model before the final
+reply is returned. The endpoint uses the Host console session cookie, so it is
+not an unauthenticated device-control endpoint.
+
+In local mode, Appium supervision is enabled by default. Host Agent probes
+`/status`, adopts a healthy existing Appium instance, starts Appium when no
+listener exists, restarts only processes it started if they crash, and stops
+those child processes on shutdown. Override `HOST_AGENT_APPIUM_*` or set
+`HOST_AGENT_DEPENDENCY_SUPERVISOR_ENABLED=false` when an external process
+manager owns Appium.
+
 ## Project Direction
 
 The durable roadmap is in [docs/ROADMAP.md](docs/ROADMAP.md). The architecture