experiment(confidence-engine): route UI journey provider centrally

app/api/cases/overview/route.js

@@ -6,7 +6,7 @@
  * Thin route pattern — no overview business logic here.
  */
 
-import { getProvider } from "@/lib/llm/provider.js";
+import { getProvider, getProviderModelName } from "@/lib/llm/provider.js";
 import { synthesizeInvestigationOverview } from "@/lib/graph/investigation-overview-synthesis.js";
 
 export async function POST(request) {
@@ -33,7 +33,7 @@ export async function POST(request) {
       { situationGraph, findings, plausibleInterpretations },
       {
         provider: getProvider(),
-        modelName: process.env.OLLAMA_MODEL ?? null,
+        modelName: getProviderModelName(),
       }
     );