feat: add manual RC release workflow

[kikoso]

Summary

• Adds a workflow_dispatch-only workflow (.github/workflows/release-rc.yml) to publish release candidates from any branch without merging to main
• Never triggers automatically — only runs when manually invoked from the GitHub Actions UI or via gh workflow run
• Updates all version files (build.gradle.kts, .release-please-manifest.json, MIGRATION.md, llm-integration-prompt.md, SKILL.md), commits and pushes to the target branch, creates a tag, and publishes a GitHub pre-release
• The existing publish.yml fires automatically on pre-release published, pushing the RC artifact to Maven Central

How to use

1. GitHub → Actions → Release RC → Run workflow
2. Set version (e.g. 4.5.0-rc.1) and branch (e.g. feat/rewrite-android-maps-utils)
3. The workflow runs from main but releases from the specified branch

Test plan

• Merge to main
• Trigger the workflow manually with a test version and a feature branch
• Verify version files are updated, tag is created, and GitHub pre-release appears
• Verify publish.yml is triggered by the pre-release

🤖 Generated with Claude Code

[googlemaps-bot]

Code Coverage

Overall Project	41.06%	🍏

There is no coverage information present for the Files changed