test: cover non-Python CLI targets

[PuneetRana7]

Summary

• Add CLI tests for an empty directory.
• Add CLI tests for a directory containing only non-Python files.
• Add CLI tests for a direct non-Python file target.
• Assert file count, score, text output, and exit code for each case.

Testing

• python -m pytest
• ruff check .
• mypy

No production behavior was changed because the existing behavior was already consistent across all three cases.
Closes #5

[Johnkothapalli]

The three CLI behavior tests match #5 and pass locally, along with Ruff lint and mypy. One required gate still fails: ruff format --check . reports tests/test_cli.py would be reformatted (missing blank separation between top-level tests, a multiline signature normalization, trailing whitespace, and no final newline).

Please run ruff format tests/test_cli.py, verify ruff format --check ., and add Closes #5 to the PR description so the accepted work is linked to its assigned issue. No production change is needed.

[PuneetRana7]

Ok i ll let u know.