Add check-pipeline-name-only-steps hook

[AmberArcadia]

Summary

• Adds a new pre-commit hook check-pipeline-name-only-steps that validates pipeline step formatting in melange YAML files
• Catches the common mistake where name: is used instead of uses: for pipeline steps (e.g., - name: test/go-fips-check instead of - uses: test/go-fips-check)
• Thanks to @OddBloke for the idea!

What it checks

The hook validates that pipeline steps don't have only a name field without uses or other details. It checks:

• Main pipeline steps
• Test pipeline steps
• Subpackage pipeline steps
• Subpackage test pipeline steps

Example of issues it catches

pipeline:
  - name: test/go-fips-check  # ❌ Should be 'uses' not 'name'
  - uses: test/go-fips-check  # ✅ Correct

Test plan

• Added test data files in test-data/ directory with examples of both valid and invalid configurations
• Tested locally with pre-commit try-repo against both good and bad YAML files
• Verified it correctly identifies all 4 types of pipeline issues (main, test, subpackage, subpackage test)

🤖 Generated with Claude Code

[dannf]

melange requires that the main package has a pipeline, so I have created packages with name-only steps. See cuda-stub-meta.yaml in extra-packages as an example. That's likely a melange bug of course, but it's reality today.