Harden automated Mac release retries

[krishagel]

Summary

• pass the manual release version through an environment variable instead of interpolating it into shell
• allow a failed release run to be retried when the existing tag already points at the same main commit
• still fail closed if that version tag points anywhere else

Verification

• pnpm exec prettier --check .github/workflows/release-macos.yml
• git diff --check

No capture or publishing behavior changes; this only hardens release orchestration.

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