Improved memory efficiency in `scripts/ci_validate_repo.py` by replacing
`read_bytes()` with chunked binary reading (64KB) for NUL byte detection.
This prevents loading entire source files into memory during CI runs.
- Consolidate file validation logic into a single loop
- Check file size before reading content to prevent loading large files into memory
- Add error handling for file reading
- Reduce I/O operations and loop iterations
This improves the efficiency of the CI validation script, especially for repositories with many files or when large files are accidentally introduced.
