Notification triage uses the intended light model tier

The built-in NotificationTriage agent had drifted from its served master and ran on the chat model tier; it now runs on the light tier as designed, making notification triage cheaper with identical results. A stale built-in /feedback skill was also removed: it filed feedback nodes of a type the platform no longer ships, so submissions were silently unusable. Feedback is owned by the Feedback module, which provides the current draft-and-submit /feedback flow.