Support Lucafile.yml as a default spec file name

[albertodebortoli]

Support Lucafile.yml as a default spec file name

Description

• Adds Lucafile.yml as a first-class default spec file name, tried after Lucafile but before prefix-discovery.
• Users who name their spec file Lucafile.yml get proper YAML syntax highlighting and editor tooling without any extra flags.
• No behaviour change for existing Lucafile users — the plain name still takes precedence.

Type of Change

• Feature

How Has This Been Tested?

• Added / updated unit tests
  • findSpecFiles_ymlExtension_returnsIt — only Lucafile.yml present → returned
  • findSpecFiles_ymlAndVariants_returnsAllSorted — Lucafile, Lucafile.yml, Lucafile-dev all returned sorted
• Manually tested locally (describe)
  • swift build — no errors or warnings
  • swift test — all tests pass

Checklist

• Swift code builds locally (swift build)
• Tests pass locally (swift test)
• Code style / formatting respected
• Documentation updated (README / comments)
• Version / tag alignment considered (if release related)

CI Considerations

• Affects build time notably
• Requires new secrets / env vars
• Alters release process

Breaking Changes?

• No

Additional Notes

SpecFinder.findSpecFiles already matched Lucafile.yml via hasPrefix("Lucafile"), so no logic change was needed there — only the exact-match short-circuit in specPath() and the updated doc comments.