ci: book-formatter pinを監査済みrevisionへ更新する

[ootakazuhiko]

Parent: itdojp/it-engineer-knowledge-architecture#266

active Book QA formatter pinを、audit 0・QA契約監査済みのimmutable full SHAへpin-only更新する。

• main/Open PR確認
• pin-only更新
• CI/review completeness
• main/Pages/HTTP
• 証跡/cleanup

[ootakazuhiko]

完了証跡

• PR: ci: update audited book-formatter pin #64
• merge SHA: 793b2c0
• review: Copilot/Codex final head、inline 0、unresolved 0、mismatch 0
• Book QA: https://github.com/itdojp/GitHub-AgentOps-book/actions/runs/29388964260
• formatter audit 0、Pages success、https://itdojp.github.io/GitHub-AgentOps-book/ HTTP 200
• active pinは監査済みSHA、cleanup完了