Replace FeedItem.priority with signals (#39)

* feat: replace FeedItem.priority with signals

Remove priority field from FeedItem and engine-level sorting.
Add FeedItemSignals with urgency and timeRelevance fields.
Update all source packages to emit signals instead of priority.

Ranking is now the post-processing layer's responsibility.
Urgency values are unchanged from the old priority values.

Co-authored-by: Ona <no-reply@ona.com>

* fix: use TimeRelevance enum in all tests

Co-authored-by: Ona <no-reply@ona.com>

---------

Co-authored-by: Ona <no-reply@ona.com>

packages/aris-core/src/reconciler.ts

@@ -72,8 +72,6 @@ export class Reconciler<TItems extends FeedItem = never> {
 			}
 		})
 
-		items.sort((a, b) => b.priority - a.priority)
-
 		return { items, errors } as ReconcileResult<TItems>
 	}
 }