fix(bd-9sm): Replace substring matching with NEEDLE event type in persistSession

persistSession() still used msg.includes('completed'/'finished'/'closed') to
find bead completion events. With NEEDLE format, msg is the event type string
(e.g. 'bead.completed'), so substring matching can misfire on
'bead.agent_completed'. Match on exact event types 'bead.completed' and
'bead.failed' instead — consistent with the fix already applied to
updateWorkerInfo() and trackTaskForHistory() in bd-vqd.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/store.ts

@@ -262,9 +262,7 @@ export class InMemoryEventStore implements EventStore {
       // Find the completion event for this bead
       const completionEvent = this.events.find(e =>
         e.bead === beadId &&
-        (e.msg.toLowerCase().includes('completed') ||
-         e.msg.toLowerCase().includes('finished') ||
-         e.msg.toLowerCase().includes('closed'))
+        (e.msg === 'bead.completed' || e.msg === 'bead.failed')
       );
 
       if (completionEvent) {