Create GitHub Copilot agent skills for CI/CD pipeline translation

Enterprises frequently standardize on different CI/CD platforms. These skills allow the agent to translate workflow definitions across platforms while maintaining secure environment variable injection and runner configurations.

## GitHub Actions to GitLab CI/CD (arcgis-port-gitlab)

Translates .github/workflows/*.yml syntax into .gitlab-ci.yml structures, mapping matrix builds, and secrets management.

Agent Execution Pattern: The agent tokenizes the source CI/CD configuration, maps syntax trees to an intermediate representation (IR), and generates the target platform syntax accompanied by a dry-run validation script.

Start by reviewing the .github/workflows/*.yml source format and the expected .gitlab-ci.yml structure. Define how matrix builds, secrets management, secure environment variable injection, and runner configurations are represented, then validate generated output with the dry-run validation script. Done means the arcgis-port-gitlab agent skill translates the stated workflow constructs between platforms.

Written by the indexing model from the issue text.