feat: back next questions with explicit graph unknowns

lib/graph/question-formulator.js

@@ -498,6 +498,16 @@ function buildBroadInvestigationQuestion(graph) {
   return `What changed during that period that could help explain why ${central}?`;
 }
 
+function isRelationshipExplanationUnknown(node, graph) {
+  const text = normaliseText(`${node?.label || ""} ${node?.description || ""}`);
+  return (
+    collectObservationNodes(graph).length >= 2 &&
+    /\b(explain|explanation|divergence|moved differently|difference between|change or event|what changed|why the observations)/.test(
+      text,
+    )
+  );
+}
+
 export function formulateTieResolutionQuestion({ graph }) {
   const comparability = assessComparability(graph);
   if (comparability.comparabilityStatus === "uncertain") {
@@ -909,7 +919,9 @@ export function formulateQuestion({ node, graph, context = {} }) {
 
   let question = investigationStrategy
     ? buildQuestionFromStrategy(investigationStrategy)
-    : buildNeutralClarificationQuestion(extractMeaning(node));
+    : isRelationshipExplanationUnknown(node, graph)
+      ? buildBroadInvestigationQuestion(graph)
+      : buildNeutralClarificationQuestion(extractMeaning(node));
 
   question = sanitizeQuestionText(question);