feat: refactor release workflow to use candidate branch

[Jacksunwei]

Summary

• Introduces release/candidate as a temporary branch for release preparation
• Release-please auto-calculates version from conventional commits (no manual version input)
• Release: Finalize workflow creates final release/v{version} branch after changelog PR merge
• Renamed all release workflows with consistent Release: prefix
• Disabled automatic GitHub release creation (manual control)

Release Flow

1. Run Release: Cut → creates release/candidate branch
2. Release: Please auto-triggered → creates changelog PR with calculated version
3. (Optional) Release: Cherry-pick to include fixes
4. Merge changelog PR → Release: Finalize creates release/v{version}, deletes candidate
5. Manually create GitHub release with tag v{version}
6. Run Release: Publish to PyPi → publishes package, creates merge-back PR

Files Changed

File	Change
release-cut.yml	New: starts release process
release-please.yml	Updated: targets release/candidate
release-cherry-pick.yml	Renamed, targets release/candidate
release-finalize.yml	New: creates final release branch
release-publish.yml	Renamed, checks out from release branch
release-please-config.json	Added skip-github-release: true

🤖 Generated with Claude Code

[gemini-code-assist]

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