fix(release): preserve historical notes compatibility

[wolfiesch]

Summary

• allow immutable historical release content to use either the legacy root-relative or current separated release-notes path
• keep the current workflow regression strict about the new publication-control/content separation

Evidence

• release run 30065487729 stopped before builds because current verification required the repair-only path inside v0.1.31
• current verifier against a freshly extracted immutable v0.1.31 tree: passed
• focused release-consistency tests: 26 passed
• mise exec node@24.13.1 -- pnpm check
• mise exec node@24.13.1 -- pnpm lint