Add changelog_body input to release workflow and document release process

[blink1073]

References

N/A

Description

Add support for providing custom release notes when triggering the release workflow, and document the full release process in CONTRIBUTORS.md.

Changes

• Add changelog_body workflow input to release.yml and pass it through to the release action
• Add "Release Process" section to CONTRIBUTORS.md with instructions for both the GitHub UI and CLI workflows (including basic release, custom changelog, and dry run examples)

Backwards-incompatible changes

None

Testing

N/A

AI usage

• Some or all of the content of this PR was generated by AI.
• The human author has carefully reviewed this PR and run this code.
• AI tools and models used: Claude Code (claude-opus-4-6)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.30%. Comparing base (2e8b042) to head (0a34837).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #418   +/-   ##
=======================================
  Coverage   90.30%   90.30%           
=======================================
  Files          51       51           
  Lines        2950     2950           
  Branches      414      414           
=======================================
  Hits         2664     2664           
  Misses        209      209           
  Partials       77       77           

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