fix(discovery): ignore empty test files

[innovationty]

Summary

• ignore .yatl.yaml and .yatl.yml files that contain only whitespace or comments during discovery
• prevent empty test files from being counted or reported as passing
• cover directory discovery, direct file discovery, and CLI output

Why

Empty test files were included in the discovered file count and then executed as empty test specifications. Filtering them during discovery keeps the reported count and output aligned with the tests that actually contain content.

Fixes #95

Validation

• pytest tests/test_run.py tests/test_cli/test_command.py::test_empty_test_files_are_ignored -q (12 passed)
• pytest --ignore=tests/test_cli/test_command.py -q (68 passed)
• ruff check .
• ruff format --check .

[Khabib73]

@innovationty Thank you so much for your excellent contribution! Your PR helps the project a lot, and I am happy to accept it. 😊 If you enjoyed working on backus (YATL), I would appreciate it if you supported us with a star on GitHub! ⭐

[innovationty]

Thank you for the kind words and I’m glad the change is helpful.I’ve starred the repository and would be happy to contribute again in the future.

[Khabib73]

welcome :)