Test/coverage

[noamteyssier]

No description provided.

[gemini-code-assist]

Code Review

This pull request significantly improves test coverage across the codebase by adding comprehensive unit tests for headers, readers, writers, records, and block indices in the bq, cbq, record, and vbq modules. It also updates StreamReader to track record IDs independently of the buffer position using a new records_read field. The review feedback identifies three key issues in the test code: a Windows-specific test failure caused by deleting a file while it is still memory-mapped, a fragile reliance on std::mem::size_of for determining serialized header sizes, and the potential for leftover temporary files on disk if tests panic. Implementing RAII guards for file cleanup and using robust serialization offsets will resolve these issues.