Function decompress_segment_pooled 

pub fn decompress_segment_pooled(compressed: &PackedBlock) -> Result<Contig>

Decompress a segment using ZSTD

Note: Decompression is less critical for pooling since:

1. Decompression contexts are smaller than compression contexts
2. Decompression happens less frequently in the hot path
3. Current implementation is adequate for now

Future optimization: Add thread-local decoder pool if profiling shows benefit