fix: make historical GitHub release backfills idempotent

[mldangelo-oai]

Summary

• Reconcile verified releases whose tagged commit predates .github/release.yml without requesting a nonexistent historical configuration file.
• Preserve configured release notes for newer tags and cover the historical replay case with a focused regression test.
• Fix the live idempotency failure: https://github.com/openai/codex-security/actions/runs/30591383965

Validation

• Reproduced the historical replay regression before applying the fix.
• Release-automation suite: 165 passing tests.
• TypeScript no-emit check and Prettier both pass.
• Independently verified the published npm package, SLSA provenance, protected publishing run, and byte-identical GitHub release asset.

[mldangelo-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 👍

Reviewed commit: bde5d7787c

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[chatgpt-codex-connector]

Security review completed. No security issues were found in this pull request.

Reviewed commit: bde5d7787c

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