feat(orchestrator): MS23-P0-005 subagent tree endpoint (#714)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/orchestrator/src/spawner/agent-spawner.service.ts

@@ -115,7 +115,13 @@ export class AgentSpawnerService implements OnModuleDestroy {
     }
 
     void this.agentIngestionService
-      .recordAgentSpawned(agentId, undefined, undefined, request.taskId, request.agentType)
+      .recordAgentSpawned(
+        agentId,
+        request.parentAgentId,
+        undefined,
+        request.taskId,
+        request.agentType
+      )
       .catch((error: unknown) => {
         const errorMessage = error instanceof Error ? error.message : String(error);
         this.logger.error(`Failed to record spawned ingestion for ${agentId}: ${errorMessage}`);

apps/orchestrator/src/spawner/types/agent-spawner.types.ts

@@ -40,6 +40,8 @@ export interface SpawnAgentOptions {
 export interface SpawnAgentRequest {
   /** Unique task identifier */
   taskId: string;
+  /** Optional parent session identifier for subagent lineage */
+  parentAgentId?: string;
   /** Type of agent to spawn */
   agentType: AgentType;
   /** Context for task execution */