Automate release pipeline with release-plz

[alongubkin]

Summary

• Replace manual release workflow with release-plz for fully automated releases
• On every push to main, release-plz opens/updates a release PR with version bump + CHANGELOG.md
• When the release PR is merged, release-plz creates a git tag, GitHub Release, and publishes to crates.io
• RELEASE_PLZ_TOKEN secret already configured

Test plan

• Merge this PR and verify release-plz opens a release PR
• Verify CI runs on the release PR
• Merge the release PR and verify tag + GitHub Release + crates.io publish

Closes ALIEN-15

🤖 Generated with Claude Code

[linear]

ALIEN-15 Automate release pipeline with release-plz

Summary

Replace the manual release process with a fully automated pipeline using release-plz.

Current process (manual)

1. Manually bump version in Cargo.toml
2. Commit and merge
3. Create a GitHub Release in the UI
4. Workflow runs cargo publish

New process (automated)

1. Merge PRs with conventional commit messages to main
2. release-plz automatically opens a release PR with bumped version + CHANGELOG.md
3. CI runs on the release PR
4. Merge the release PR
5. release-plz creates git tag, GitHub Release, and publishes to crates.io

Changes

• Delete .github/workflows/release.yml (old manual workflow, would cause double-publish)
• Create .github/workflows/release-plz.yml (two jobs: release-pr + release)
• Create release-plz.toml (release-plz config)
• Create cliff.toml (git-cliff changelog format config)
• Add RELEASE_PLZ_TOKEN secret (GitHub PAT for triggering CI on release PRs) — already done

[greptile-apps]

Your free trial has ended. If you'd like to continue receiving code reviews, you can add a payment method here.