CI/CD User Docs with Troubleshooting and Examples

What does this issue propose? Propose a batch of 4 documentation improvements to enhance CI/CD user guides for better clarity and usability. These address gaps in troubleshooting, permissions, and configuration examples for pipelines. For Hacktoberfest/hackathon-2025.

Proposed Changes:

1. /doc/user/project/pipelines/job_artifacts.md: Add troubleshooting for "Waiting for Resource" errors with resource group YAML examples.
2. /doc/user/project/pipelines/runners.md: Clarify role-based permissions for shared runner assignment in project settings.
3. /doc/user/project/pipelines/settings.md: Update pipeline rate limiting notes with admin UI steps and examples.
4. /doc/user/project/pipelines/variables.md: Add examples for dynamic CI variables using shell scripts.

Why? These improve user experience for common CI/CD tasks, addressing feedback on missing configs and unclear permissions. Quick wins for #hackathon-2025.

Related Files:

• /doc/user/project/pipelines/job_artifacts.md
• /doc/user/project/pipelines/runners.md
• /doc/user/project/pipelines/settings.md
• /doc/user/project/pipelines/variables.md

Labels: documentation ~"technical writing" ~"hackathon-2025" ~"good first issue" ~"contributor"