🐛[Fix] Allow release promotion commit validation

[maruson08]

Problem

The v2.1.0 promotion range from main contains eight published human-authored commits created before commit-message enforcement. Validating the entire range would block the release even though the workflow explicitly preserves that history and prohibits rewriting it.

Fix

This change adds an explicit grandfather boundary at edb0ade331c54f380ae33abe7816c5a92f3a590a, the final v2.1 commit before enforcement. Range validation excludes ancestors through that boundary while continuing to validate every later human-authored non-merge commit. Merge commits remain excluded by topology, and PR-title and branch-policy checks are unchanged.

Verification

• Accepted and rejected message cases pass
• Synthetic Git history proves a non-conforming published ancestor is excluded while a later compliant commit is validated
• origin/v2.1..HEAD validates the fix commit
• The prospective origin/main..HEAD release range validates four post-enforcement commits
• npm test
• npm run build
• node tests/ocr-smoke.test.mjs
• git diff --check

Closes #83 after merge into v2.1.

This PR contains no product, version, tag, release, deployment, or history-rewrite change. It must be merged and reverified before the v2.1.0 promotion PR is created.