ci: CD auto-deploy via workflow_run trigger

- deploy.yaml now triggers automatically after successful CI completion
- Adds workflow_run event listener for 'CI - Build & Test'
- Guards deploy to only run when CI conclusion == success
- Preserves manual workflow_dispatch for targeted deploys
- Adds CI/CD note to README

README.md

@@ -3,6 +3,8 @@
 Nexus is the operations platform for the Noveria ecosystem. OpenClaw is an
 adapter-backed agent runtime, not a dependency of the frontend or domain model.
 
+> CI/CD auto-deploy enabled — every push to main triggers build → test → deploy.
+
 ## Current foundation
 
 - Vue 3, TypeScript, Pinia, Vue Router and Tailwind CSS