refactor(skills): clean skill names (strip NN- prefix from name:) — convention change

Adopt: directory keeps its NN- ordering prefix; skill `name:` is the clean form
without it (dir 16-seo-schema-validator → name: seo-schema-validator). Nicer to
invoke, matches the original desktop/SKILL.md names, still globally unique.

- 71 root SKILL.md: name: NN-foo → name: foo (flat skills + reference-curator suite).
  Plugins (mac-optimizer/multi-agent-guide/dintel-bootstrap) already clean; 95 already clean.
- scripts/migrate_skill_root.py: derive name = dirname minus NN- prefix (skill_name()).
- CLAUDE.md + SKILL-MIGRATION-GUIDE.md: document the dir-prefix / clean-name convention.

verify_skills.py: 0 name collisions across all renamed skills. (The ~/.claude/skills
symlinks were re-pointed to the clean names separately — filesystem only.)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

custom-skills/42-jamie-faq-entry/SKILL.md

@@ -1,5 +1,5 @@
 ---
-name: 42-jamie-faq-entry
+name: jamie-faq-entry
 description: "카카오톡 플러스 채널 Kanana 상담매니저 Q&A 답변 생성 및 검토 스킬. 제이미성형외과의 카카오톡 채널에 등록할 고객 문의 질문과 답변 엔트리를 생성, 검토, 수정합니다. 의료광고 심의 준수, 브랜드 보이스 일관성, 카카오 카나나 가이드 규격을 모두 반영합니다. Triggers: 카나나 답변, Kanana Q&A, 카카오톡 챗봇, 카카오 상담 답변, 챗봇 문답, 자동답변 등록, 카나나 엔트리, chatbot QA, KakaoTalk channel reply, 카카오 자동응답. jamie-marketing-editor 및 jamie-brand-guardian 스킬과 연계하여 사용합니다."
 ---