feat(agent): Adds prologue functionality (#9336)

### What problem does this PR solve?

feat(agent): Adds prologue functionality #3221

- Add a prologue field to the IInputs type
- Initialize the prologue state in the chat container
- Use useEffect to monitor prologue changes and add prologue responses
### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

web/src/pages/agent/interface.ts

@@ -38,4 +38,5 @@ export type IInputs = {
   avatar: string;
   title: string;
   inputs: Record<string, BeginQuery>;
+  prologue: string;
 };