fix(support): agent-demo self-seeds (join default queue + go online); tickets always get a queue

Root cause of 'waiting for escalations': no queue/membership meant tickets were
never assigned. Now: createTicket find-or-creates a default queue; new joinDefault
endpoint + useGoOnline hook; agent-demo joins+goes-AVAILABLE on load (assignPending
picks up any waiting ticket). smoke-support self-seeds (no seed script needed).
Also: vitest singleFork to end cross-file DB races (45 tests deterministic).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-kernel-client/src/rest.ts

@@ -87,6 +87,9 @@ export class RestClient {
   async joinQueue(queueId: string): Promise<unknown> {
     return this.post('/v1/support/queues/' + queueId + '/members', {});
   }
+  async joinDefaultQueue(): Promise<unknown> {
+    return this.post('/v1/support/agents/me/join', {});
+  }
   async setAvailability(state: string): Promise<unknown> {
     const r = await fetch(this.url('/v1/support/members/me/availability'), {
       method: 'PATCH',