docs: reshape runbooks into .agents/skills/<name>/SKILL.md (phase 4)

Problem: runbooks are agent-executable procedures but lived at the repo root,
separate from the other agent instruction now under .agents/.

Change:
- Move runbooks/<name>.md -> .agents/skills/<name>/SKILL.md (folder per skill,
  matching the wiki-hq skills layout). Frontmatter (name, risk_class, inputs,
  verification, docs_update_checklist, transition) preserved.
- Rewrite links (inbound from plans; between-skill siblings) via the move map.
- Update prose references in AGENTS.md, HERMES.md, .agents/OIKOS.md, and the
  operations schema; fix a pre-existing stale link to operations/commands.md.

No code consumed runbooks/ by path, so nothing else changes.

Verification: all SKILL.md frontmatter parses with valid risk_class; every
lifecycle transition resolves to an oikos/ontology.yaml state; broken-link
count 127 -> 126 (fixed one, introduced none).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

HERMES.md

@@ -19,8 +19,8 @@ When in doubt, check `/opt/homelab-context/` first.
 
 For the canonical workflows (service health check, config change +
 deploy, client enrollment, incident investigation, and each node
-lifecycle transition), read the matching file in `runbooks/*.md` before
-acting. Each runbook carries its risk class, required inputs, the
+lifecycle transition), read the matching `.agents/skills/<name>/SKILL.md` before
+acting. Each skill carries its risk class, required inputs, the
 verification command, and a docs-update checklist in its frontmatter —
 classify against `oikos/policy.yaml` using that risk class before any
 mutation. Don't re-derive topology or the mutation path by grepping the