Add GitLab and Bitbucket packages

[paladini]

Summary

• extract shared runtime and CLI while preserving the GitHub Action entrypoint
• add GitLab CI/CD Component and Bitbucket Pipe packaging
• add GitLab and Bitbucket platform adapters plus marketplace docs/spec updates

Verification

• npm run all
• npm audit --omit=dev

Notes

• Docker CLI is installed locally, but Docker Desktop daemon was not running, so the OCI image smoke build still needs to be run in an environment with Docker daemon available.