Docs: add a practical single-node monitoring guide for Arc nodes on Ubuntu

[Bela1401]

Hi team,

I’ve successfully deployed and monitored a single Arc node on Ubuntu x86_64 bare-metal using the Arc execution and consensus metrics endpoints together with Prometheus and Grafana.

While the repository already contains monitoring assets, the current setup appears to be oriented more toward localdev / multi-node environments. I think it would be helpful to add a practical single-node monitoring guide for operators running one execution layer and one consensus layer on the same host.

The guide I’d like to contribute would cover:

• Prometheus scrape targets for a single node
• Grafana setup reusing the official Arc dashboards
• local-only binding for monitoring services
• SSH tunnel access
• troubleshooting notes for common issues, including:
  • Prometheus permission errors on /prometheus/queries.active
  • confusion around 127.0.0.1 bindings vs public IP access

If this sounds useful, I’d be happy to open a docs PR.

[ZhiyuCircle]

That sounds useful, few suggestions:

• For placement, docs/monitoring.md (or similar), alongside the existing docs/running-an-arc-node.md and docs/installation.md.
• There are scrape template is in crates/quake/templates/ if you want to reference it.
• For scope: Your proposed scope LGTM, just keeping it focused on a single EL + CL on one host for operators running

Feel free to open the PR whenever you are ready.

[Bela1401]

Opened PR #28 for the monitoring docs update.

I kept it aligned with the guidance above:

• new docs/monitoring.md
• scoped to a single-host EL + CL operator setup
• added a reference from docs/running-an-arc-node.md

Please let me know if you would like any refinements and I can update it quickly.