continue scaffolding and refine the basic foundation

server/types/chat.ts

@@ -1,4 +1,5 @@
 export type MessageType = 'system' | 'agent' | 'user';
+export type GenerationStatus = 'pending' | 'active' | 'completed' | 'failed';
 
 export interface ChatMessage {
     type: MessageType;
@@ -8,19 +9,21 @@ export interface ChatMessage {
 export interface GenerateRequestBody {
     topicId: string;
     messages: ChatMessage[];
+    regeneratesFrom?: string;
 }
 
 export interface GenerationStreamEvent {
-    type: 'token' | 'complete' | 'error';
+    type: 'start' | 'token' | 'complete' | 'error';
     data: string | object | null;
 }
 
-export interface GenerationStatus {
+export interface GenerationStatusResponse {
     generationId: string;
-    status: 'pending' | 'active' | 'completed' | 'error';
+    status: GenerationStatus;
     content?: string;
     topicId?: string;
     model?: string;
     tokensGenerated?: number;
     tokensUsedThinking?: number;
+    error?: string;
 }