feat(agent): POST timeline events to vibn-frontend ingest API

- vibn-events-ingest.ts + emit() dual-write with session PATCH
- .env.example: VIBN_API_URL, AGENT_RUNNER_SECRET

Made-with: Cursor

.env.example

@@ -45,5 +45,12 @@ WORKSPACE_BASE=/workspaces
 # Internal URL of this service (used by spawn_agent to self-call)
 AGENT_RUNNER_URL=http://localhost:3333
 
+# Base URL of the vibn-frontend Next app (runner PATCHes sessions + POSTs timeline events)
+# Production: https://vibnai.com  (must be reachable from this container)
+VIBN_API_URL=http://localhost:3000
+
+# Same value as AGENT_RUNNER_SECRET on the Next app (ingest + session PATCH)
+AGENT_RUNNER_SECRET=
+
 # Optional: shared secret for validating Gitea webhook POSTs
 WEBHOOK_SECRET=