Route diffs to DiffCompressor via Magika label mapping

Remove LLMLingua: Kompress is the sole text compressor

Reduce compression latency: cache serializations, eager-load all compressors, fix Magika, bump to 0.5.5

Fix mypy errors and add network timeout handler for flaky CI tests

Fix mypy type errors for Python 3.12 compatibility

Fix mypy type errors in compression module

Add universal compression module with ML-based content detection