Mn9Al7C2 P4/mmm — H1 Mn-Al-C GGen candidate (62 meV/atom)

Single source of truth for the rare-earth-free permanent magnet discovery program (quest 01a06c81). One row per (candidate, attempt). Schema follows skills/discovery-loop.md: property columns carry values only with action receipts in actionids; stage/status enums gate tier-2 spend; ciffileid is a file-asset reference. Excluded elements: La through Lu, Sc, Y. Row hypothesisid='schema-v1' is a schema probe, not a candidate.