Bound the biochar electron-transfer model separately from removal endpoints #1740

CommunityMech:000291; PMID42139785. Preserve all three nodes, both directions and reported removal/mineralization outcomes. Electrochemical and multi-omics findings support the authors electron-transfer and circuit interpretation, with the route and individual mediators qualified by abstract-only access. Retain PARTIAL SYNTROPHY on the two mechanism nodes: the local enum explicitly does not assert obligacy. Keep the measurement endpoint distinct and untyped; use canonical collective participants for the circuit and endpoint. No new genetic design or optimization. Close only after protected-main merge.

Precommit correction: adversarial reading of the schema caught the original issue rationale wrongly requiring obligacy. The initial 816-test report is archived as superseded. Append-only correction histories, a schema-contract regression and a fresh full validation record the correction.

Dedup:1006 all-state issue titles/bodies searched by IDs, PMIDs, names and broad substrate/taxon aliases. All nine matching bodies read; none is this graph repair. Explicitly read529/573/605 for general source/panel/membership scope.49 local matching files found with ignored/hidden included; .git/docs/site/references_cache excluded, relevant caches separately inspected. Comments and PRs not exhaustive. Self-adversarial review, not independent approval.