Diagnoses the root cause of the persistent pattern from 59B.2-59B.4
where explicit dual-option input collapsed into a single undifferentiated
unknown node. Concludes the graph vocabulary lacks first-class primitives
for options/decisions (not primarily a prompt issue). Identifies three
missing primitives: option node kind, decision node kind, alternative_of
edge type. Recommends ~25-line schema addition for 60A.2 implementation.
