feat: P4.6 agent demo + escalate button + support seed/smoke (P4 complete)

apps/agent-demo (Vite): agent sets AVAILABLE, sees assigned tickets, opens the
thread, replies. message-demo customer pane gains 'escalate to support' (via
SupportProvider/useEscalate). seed-support + smoke-support prove the loop:
escalate -> auto-assign -> agent reply -> customer receives. 45 tests; realtime/
inbox/support smokes all pass; both demos build.

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

apps/agent-demo/vite.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+
+export default defineConfig({
+  plugins: [react()],
+  server: { port: 5174 },
+});