feat: session source in session_meta and an Automated sidebar folder (#40)

Co-authored-by: Alice <alice@prismshadow.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/core/src/omnimessage/types.ts

@@ -92,6 +92,8 @@ export interface SessionMetaPayload {
   agent_state: string;
   /** Absolute path to the Workspace. */
   workspace: string;
+  /** Session origin: spawned by a subagent / triggered by a scheduled task; absent = user-created. */
+  source?: "subagent" | "schedule";
 }
 
 // ---------------------------------------------------------------------------