checkpoint: preserve semantic decomposition investigation state

lib/graph/orchestrator.js

@@ -343,7 +343,7 @@ function buildUpdateDiagnostics({
   };
 }
 
-export async function startCase(body) {
+export async function startCase(body, dependencies = {}) {
   const parsedRequest = startCaseRequestSchema.safeParse(body);
 
   if (!parsedRequest.success) {
@@ -399,8 +399,12 @@ export async function startCase(body) {
   const graphReferenceValidation = validateGraphReferences(
     initialSituationGraph,
   );
-  const initialQuestionResult = determineGraphBackedQuestion({
+  const provider = dependencies.provider ?? getProvider();
+  const modelName = dependencies.modelName ?? analysis?.modelName ?? null;
+  const initialQuestionResult = await determineGraphBackedQuestion({
     situationGraph: initialSituationGraph,
+    provider,
+    modelName,
   });
   const situationGraph = initialQuestionResult.success
     ? initialQuestionResult.updatedSituationGraph