Ring deployments for sklils

### Feature summary

_No response_

### What problem are you trying to solve?

Currently if we do roll out skills we make all of them available for everyone. We can't text out new skills without affecting all users

### Proposed solution

Staff-gated skills

### Workflow impact

_No response_

### Installation context

_No response_

### Additional context

_No response_

No files, tests, or entry points are identified in the issue. Start by clarifying how skills are represented and where availability is controlled, then define the staff-gated rollout workflow and its verification criteria before locating the relevant implementation and tests.

索引モデルが issue の本文から書いたものです。