feat(agent): add pressure trend demo

docs/agent-ui-protocol.md

@@ -21,6 +21,16 @@ data: {
 
 ## Envelope Types
 
+Current `agent-ui@1` support is intentionally limited to three trusted shapes:
+
+- `registered_component` for frontend-registered business panels.
+- `chart` for the `echarts-safe-subset` chart grammar.
+- `map_action` for the WebGIS map adapter.
+
+The Agent must not return executable JS, JSX, HTML, CSS, or arbitrary component
+source. The frontend renders only allowlisted components, chart specs, and map
+actions.
+
 ```ts
 type UISurface = "chat_inline" | "side_panel" | "canvas" | "map_overlay";
 
@@ -62,6 +72,11 @@ GET /api/v1/agent/chat/ui-registry
 The registry returns the allowed chart grammar, registered components, and map
 actions. Unknown components/actions should be rejected by the frontend.
 
+`map_action` is a WebGIS-specific extension, not a general command channel. It
+is valid only on `map_overlay`; every action and parameter set must be validated
+by the frontend before it can affect MapLibre state. Invalid map actions should
+fall back to `fallbackText`.
+
 Initial mappings:
 
 - `show_chart` -> `chart`