refactor: Unify streamId and conversationId handling for improved job management

- Updated ResumableAgentController and AgentController to generate conversationId upfront, ensuring it matches streamId for consistency.
- Simplified job creation and metadata management by removing redundant conversationId updates from callbacks.
- Refactored abortMiddleware and related methods to utilize the unified streamId/conversationId approach, enhancing clarity in job handling.
- Removed deprecated methods from GenerationJobManager and InMemoryJobStore, streamlining the codebase and improving maintainability.

packages/api/src/stream/interfaces/IJobStore.ts

@@ -89,12 +89,9 @@ export interface IJobStore {
     conversationId?: string,
   ): Promise<SerializableJobData>;
 
-  /** Get a job by streamId */
+  /** Get a job by streamId (streamId === conversationId) */
   getJob(streamId: string): Promise<SerializableJobData | null>;
 
-  /** Find active job by conversationId */
-  getJobByConversation(conversationId: string): Promise<SerializableJobData | null>;
-
   /** Update job data */
   updateJob(streamId: string, updates: Partial<SerializableJobData>): Promise<void>;