fix(assessors): FileSizeLimitsAssessor now respects .gitignore

[chambridge]

Description

Refactored FileSizeLimitsAssessor to use git ls-files instead of glob() to enumerate source files. This ensures that files in .gitignore'd directories (like .venv/, node_modules/) are not scanned, which was causing false failures when large vendored files exceeded the line count thresholds.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test coverage improvement

Related Issues

Fixes #245

Changes Made

• Refactored FileSizeLimitsAssessor.assess() to use git ls-files instead of pathlib.glob() for file discovery, ensuring .gitignore rules are respected
• Added graceful fallback to rglob() for non-git repositories
• Added safe_subprocess_run import from subprocess_utils for secure subprocess execution with timeout
• Added 5 new unit tests for FileSizeLimitsAssessor covering gitignore behavior, edge cases, and scoring logic

Testing

• Unit tests pass (pytest)
• Integration tests pass
• Manual testing performed
• No new warnings or errors

Checklist

• My code follows the project's code style
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes