ci: improve automated release notes

[adlio]

Summary

• keep the existing tag-driven GitHub release automation in schema
• make release notes extract the matching version entry from README version history
• fall back to git-log-based notes when a README entry is missing so releases still complete

Test Plan

• python3 README extraction script for v1.4.0
• /tmp/actionlint-bin/actionlint .github/workflows/release.yml

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.79%. Comparing base (f29e00c) to head (f1149dc).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #49   +/-   ##
=======================================
  Coverage   99.79%   99.79%           
=======================================
  Files          10       10           
  Lines         483      483           
=======================================
  Hits          482      482           
  Misses          1        1           

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