feat: improve chat retrieval, message versions and Markdown rendering

frontend/src/contracts/index.ts

@@ -69,6 +69,8 @@ export interface Conversation {
 }
 
 export interface ChatMessage {
+  activity?: Array<{ type: 'thinking'; text: string } | { type: 'tool'; tool_call_id: string }>
+  versions?: string[]
   message_id: string
   conversation_id: string
   role: 'user' | 'assistant' | 'system'
@@ -81,6 +83,7 @@ export interface ChatMessage {
 }
 
 export interface Citation {
+  citation_id?: string
   note_id: string
   block_id: string
   file_path: string