Add CreateWorkItemNote tool

Problem to solve

We should add a tool to Duo Workflow to allow creating notes (comments) on work items via the Duo Workflow.

Security Consideration

As noted in this discussion, allowing free-form comments introduces the risk of triggering GitLab quick actions (e.g., /merge, /close, /assign, etc).

We must include a safeguard to detect and reject any comment that contains a GitLab quick action. We already apply this logic in the create_merge_request_comment tool and should reuse or adapt the same validation here.