Fix TypeScript error: Add 'environment' source type to CommandObservation

- CommandObservation interface now includes 'environment' as a valid source
- This allows setup script observations to be properly typed in the frontend
- Fixes TypeScript compilation error in chat-interface.tsx

Author: openhands-agent

frontend/src/types/core/observations.ts

@@ -11,7 +11,7 @@ export interface AgentStateChangeObservation
 }
 
 export interface CommandObservation extends OpenHandsObservationEvent<"run"> {
-  source: "agent" | "user";
+  source: "agent" | "user" | "environment";
   extras: {
     command: string;
     hidden?: boolean;