v181: shipped lead raised TypeError on the platform's own compress_messages call shape; 28/28 fixed, outputs byte-identical, tokens unchanged at 278973

v41: fixed silent message deletion in 6 legacy compressors; message-count invariant pinned across all 11; 147 tests

v14: order-sensitive coherence metric + COACH configs (adaptive_structural 83.44% @ 0.8723)