docs: Add synopsis to CI/CD pipeline and job commands
Description
This change adds helpful descriptions to several GitLab CLI commands that previously had empty help text. The updates explain what each command does and highlight useful options like --dry-run for previewing changes before making them, --live for real-time updates, and --status for filtering results. These descriptions will make the commands more user-friendly by providing guidance on how to use key features when someone runs the help command.
Content follows the documentation style guide and the GitLab CLI (glab) documentation style guide.
Related issues and merge requests
Edited by Brendan Lynch