a5ca0e7481
An unknown select rule in a process document now refuses with the accepted vocabulary beside the quoted offending value: block std::sweep: unknown select rule "plateau" (accepted: argmax | plateau:mean | plateau:worst) mirroring the roster-naming metric-refusal shape. The roster is derived from slot_kind_label(SlotKind::SelectRule) — CLI describe output and the document refusal stay in sync by construction — and a companion test pins the "select rule: " prefix that derivation trims, so a label-wording drift breaks a test instead of silently degrading the prose. No alias-hint sentence: the enumeration alone rescues the bare-plateau paste case (fieldtest df_3), and the document schema stays strict per #300 F7.