AI features in early access

AI chat, the pipeline builder and the CI fix agent enter early access, switched off until they are enabled for a workspace.

• AI chat, the pipeline builder and the CI fix agent are built and deployed in early access. They are switched off and are not available to customers yet.
• The pipeline builder writes GitHub Actions workflows and delivers them as a pull request. Its jobs run on Runzivo only after the workspace approves them.
• The CI fix agent proposes changes to CI files for a failed run in a pull request from a new branch. It never pushes to an existing branch and never merges.