Design and deliver CLI documentation style guide
## Overview
Design and deliver a CLI documentation style guide for the `glab` CLI, establishing consistent structure, style, and user expectations across all CLI documentation.
## Objectives
### Review existing CLI docs
- [x] Audit the [CLI documentation](https://docs.gitlab.com/cli/) to identify alignment opportunities across structure, style, and user expectations.
- [x] Review the [`gitlab-org/cli`](https://gitlab.com/gitlab-org/cli) project for recent MRs that clarified CLI options or experimental feature messaging.
### Define purpose and audience
- [x] Define the purpose and target audience for a new CLI docs style guide page. Consider two primary audiences:
- [x] **Contributors**: Guidance for contributors across stages.
- [x] **Reviewers**: Technical writers or other reviewers of new CLI docs pages or updated pages.
### Draft the style guide
- [x] Use GitLab Duo to generate a first draft of the new CLI docs style guide.
- [x] Check for accuracy and carry out initial review.
### Review
- [x] Request review from `@phikai` and `@timofurrer`
- [x] Identify and request relevant Technical Writers for review
### Merge
- [x] Address review feedback and merge the page.
- [x] Add navigation item for new page.
### Communicate
- [x] Share new page with relevant Slack channel groups.
## Related
- Stage lead planning issue: https://gitlab.com/gitlab-org/technical-writing/team-tasks/-/work_items/1576
issue