Relation kinds are inverse pairs — one stored string can't speak from both seats

[mpstaton]

Context:

• Relation-Kinds-Are-Inverse-Pairs

Operator ruling to log (not fix yet): kinds like funder_of/funded_by are inverse pairs and need representing both ways. Current KIND_INVERSE read-map covers only the funder pair; hierarchical kinds (initiative_of from the parent's seat) and future directional kinds inherit the defect. Three design options recorded in the issue file.