chore: remove GitHub Actions cloud runtime (workflow, scripts, docs) (#443)

Remove the 'OpenChamber for Actions' feature that ran OpenChamber on
GitHub runners via Cloudflare/Ngrok tunnels. This was a separate
deployment target with its own lifecycle scripts and documentation
that added maintenance overhead without benefiting local usage.

Deleted:
- .github/workflows/opencode.yml (Actions workflow)
- scripts/monitor.sh (service self-heal loop)
- scripts/persistence-save.sh (artifact encryption/upload)
- scripts/persistence-restore.sh (artifact decrypt/restore)
- scripts/opencode-config.sh (Actions config bootstrap)
- docs/OPENCHAMBER_FOR_ACTIONS.md (user guide)

Updated:
- README.md: removed 'GitHub Actions (Cloud Usage)' section

Local Cloudflare Quick Tunnel support (--try-cf-tunnel) is unaffected.

README.md

@@ -80,16 +80,6 @@ The whole project was built entirely with AI coding agents under my supervision.
 - In-extension settings, responsive layout, and theme mapping that matches your editor
 - Hardened runtime lifecycle and health checks for faster startup and fewer stuck reconnect states
 
-### GitHub Actions (Cloud Usage)
-
-Run OpenChamber remotely using GitHub Actions. No local computer required.
-
-*   **Zero Setup:** Runs on GitHub's infrastructure.
-*   **Persistence:** Optional; enabled when `OPENCODE_SERVER_PASSWORD` is set (encrypted).
-*   **Remote Access:** Access via secure tunnel (Cloudflare/Ngrok).
-
-[**Read the Guide: OpenChamber for Actions**](docs/OPENCHAMBER_FOR_ACTIONS.md)
-
 ### Custom Themes
 
 Create your own color schemes by dropping JSON files into `~/.config/openchamber/themes/`. Hot reload supported — no restart needed.