docs(runbooks): add runbook spec, template, index and 6 first-batch runbooks; light-enhance existing 10

- RUNBOOKS.md: repo-level spec (six-field model, naming, safety, maturity path)
- runbooks/_template.md + README.md: standard template and 16-entry routing index
- new: issue-to-merge, fix-ci, release, rollback, network-change, network-recovery
- light-enhance 10 existing runbooks with Purpose/Scope/Safety headers
- AGENTS.md: point step 3 at index/spec, add runbook execution rules
- docs/agent-runbook-guide.md: archive of Manus AI guide

runbooks/rustdesk-health.md

@@ -1,5 +1,14 @@
 # RustDesk server health (hk2)
 
+## Purpose
+
+Read-only health check of the `/opt/rustdesk` server stack.
+
+## Scope
+
+- Applicable: [hk2.chans.xyz](../hosts/hk2.chans.xyz.md), `/opt/rustdesk`.
+- Read-only: does not change RustDesk configuration or service state.
+
 Read-only checks for the `/opt/rustdesk` stack on **hk2.chans.xyz**.
 
 Facts: [hosts/hk2.chans.xyz.md](../hosts/hk2.chans.xyz.md)
@@ -66,6 +75,11 @@ The sanitized Ansible health profile is `rustdesk` (deployed via
 locally through `vps-healthcheck.timer`, writes a sanitized JSON result to
 `/var/lib/vps-health/latest.json`, and never exposes secrets.
 
+## Safety
+
+- Read-only: never mutate configuration or service state during this check.
+- If live state conflicts with an expected value, `STOP` and report.
+
 ## After config changes
 
 Reviewed changes to `/opt/rustdesk/compose.yml` (relay address, image pin, port