docs(agents): point the Skills section at #14's human-merge reservation

A seat working on a skill lands in the Skills section, not in the Prime
Directives. It described both roots and said nothing about their merge
posture. One class pointer, no second enumeration.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XqDQYVU5smx29ts9pAErja

Author: claude

AGENTS.md

@@ -650,6 +650,9 @@ agent playbooks live in `.claude/skills/` and must carry `metadata.internal: tru
 `dogfood-verification` (boot and drive the real app in a browser) and
 `spec-property-retirement` (ADR-0049 enforce-or-remove — the full retirement kit).
 
+⛔ **Both roots are governed surfaces**: a PR touching either is human-merge only and may
+never be queued or armed — **Prime Directive #14**, machine-enforced, not advisory.
+
 ---
 
 ## Patterns