Add test coverage for BodyValidator edge cases (empty/leading-blank messages) #490

Description

The BodyValidator (commit_check/engine.py) should be tested for edge cases involving leading blank lines and whitespace-only messages.

Note: _get_commit_message() (line 127) strips the input before it reaches BodyValidator.validate(), so leading blank lines are removed early. The following tests verify the actual behavior.

Goal

Add test cases in tests/engine_test.py under the existing TestBodyValidator class to cover:

1. Message with leading blank lines and body content (e.g. "\n\nbody content") — should FAIL (message without subject won't pass require_body)
2. Message with leading blank lines and no body content (e.g. "\n\n") — should PASS (empty after strip, treated as no commit message)
3. Message with only whitespace lines (e.g. " \n ") — should PASS (same as above)

These tests will bring coverage to 100% for the BodyValidator.validate() method.

How to verify

pytest tests/engine_test.py::TestBodyValidator -v

Coverage can be checked with:

coverage run -m pytest tests/engine_test.py::TestBodyValidator
coverage report -m

References

• commit_check/engine.py — BodyValidator class (lines 530–564)
• tests/engine_test.py — TestBodyValidator class (existing tests start at line 915)