Added Rar_StreamValidation_ThrowsOnTruncatedStream test that verifies InvalidOperationException IS thrown when a RAR stream ends prematurely (position < expected length). Created TruncatedStream mock to simulate corrupted/truncated RAR files. This test validates the exception condition (_position < Length) works correctly.
Co-authored-by: adamhathcock <527620+adamhathcock@users.noreply.github.com>
