Strengthen validation retries and checkpoint safety

internal/modules/dnd/validate/npcoccurrences/registry/validator.go

@@ -105,9 +105,10 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 
 func rejection(issues []string) contracts.ValidationResult {
 	return contracts.ValidationResult{
-		Approved:   false,
-		ReasonCode: ReasonCode,
-		Message:    diagnostics.Aggregate("invalid NPC occurrence registry", issues),
+		Approved:           false,
+		ReasonCode:         ReasonCode,
+		Message:            diagnostics.Aggregate("invalid NPC occurrence registry", issues),
+		CorrectionGuidance: "Return NPC occurrences using contextual NPC names that match an NPC in the supplied registry; omit occurrences that cannot be matched unambiguously.",
 	}
 }