Make conversation queues mutually exclusive

tests/web/conversations-route.test.ts

@@ -599,7 +599,7 @@ describe('conversations route', () => {
       expect(body.flagged).toEqual([expect.objectContaining({
         // Flags carry the owned id so the dashboard can match its list rows.
         conversationId: `${encodeURIComponent('@t2_one:reddit.com')}~room-alice`,
-        username: 'alice', source: 'keyword', killed: true,
+        username: 'alice', source: 'funnel', killed: true,
       })]);
       // The keyword hit never reaches the model; only the clean row is screened.
       expect(ai.screenConversationsForSellers.mock.calls[0][0]).toEqual([