Bound MDSC composition-mediated glycan degradation and cross-feeding labels #1623

Mucin_Glycan_MDSC_Synthetic_Gut_Community: full PMID42109165 supports causal effects of substrate regimes on composition, degradation and metabolites. Existing composition-to-degradation arrow needs PARTIAL mediation boundary because substrate changes both, not a composition-only intervention. Preserve specific glycan effects and the BSM O-glycan versus N-glycan distinction. Pool measurements do not resolve member-specific exchange. Preserve closed957/958/959 fixes and existing pairwise knowledge gap; no invented pairwise topology.

Dedup:906 all-state issue titles/bodies; ignored/hidden-inclusive local search with explicit docs/site/cache/git exclusions,31 matching files. No exhaustive PR-comment audit. Self-adversarial review, not independent approval. Close only after protected-main merge.