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>

.agents/skills/lifecycle-destroy-node/SKILL.md

@@ -0,0 +1,42 @@
+---
+name: lifecycle-destroy-node
+risk_class: destructive
+inputs: [node_name]
+verification: "homelab node <name> relations returns unknown-entity; pct list on the backend no longer shows it"
+docs_update_checklist: [archaeology_entry, containers_index_update]
+transition: "deprecated -> destroyed"
+---
+
+# Lifecycle: destroy a node
+
+**Destructive.** Requires operator approval + typed confirmation phrase
+per `oikos/policy.yaml`. Requires (ontology): backups verified, secrets
+recipients removed + re-keyed, ingress/DNS removed, archaeology entry,
+ledger entry.
+
+1. Confirm the node is `deprecated` with zero `affected_by` edges
+   (`homelab node <name> relations`) — do not skip this even if the
+   deprecation runbook was followed recently; state can drift.
+2. If it's an enrolled client: `homelab client remove <name>` — revokes
+   the age key, re-keys SOPS, removes the inventory entry. This is
+   already destructive-class and confirmed in the CLI.
+3. Remove any ingress route (Caddy config repo) and DNS record still
+   pointing at it.
+4. Verify backups of anything on it are retained per policy before the
+   disk goes away (see `backs-up-to`).
+5. Destroy the LXC/VM (`pct destroy` / `qm destroy`).
+6. Move the `hosts.<name>:` block (if any inventory remnant survives
+   `client remove`, e.g. infra-only LXCs with no age key) into
+   inventory.yaml's `archaeology:` section: `pve_id`, `destroyed` date,
+   `reason`. Add a row to `containers/index.md` "Recently destroyed"
+   table (kept for human-readable browsing alongside the structured
+   data).
+7. `oikos/ledger.py append host:<name> destroy destructive --result ok`.
+8. Regenerate: `python3 mcp/build_host_files.py && python3
+   oikos/gen-topology.py` — the node drops out of `hosts/*.yaml` and
+   appears in the topology doc's archaeology table.
+
+If the destroy fails partway (e.g. secrets revoked but pct destroy
+errors), do not re-run step 2 — `client remove` is not idempotent
+against a second revocation attempt on the issuance server. Finish the
+remaining steps manually and note the partial state in an investigation.