Refresh live model catalog when a harness session becomes active

src/App.tsx

@@ -1000,6 +1000,18 @@ export default function App({
   }
   const busySessionIds = busySessionIdsRef.current;
 
+  /** Probe the active session's harness for its live model catalog whenever
+   * the active harness changes. Catalogs load lazily (probing spawns a CLI
+   * process) and the boot refresh runs before restored sessions land, so a
+   * fresh session would otherwise show only the built-in fallback model
+   * until the picker happened to be opened. Idempotent: refreshHarnessCatalogs
+   * dedupes via hasLiveCatalog and its inflight map. */
+  const activeHarness = active?.harness;
+  useEffect(() => {
+    if (!activeHarness || !isLiveHarness(activeHarness)) return;
+    void refreshHarnessCatalogs([activeHarness]);
+  }, [activeHarness]);
+
   const usageProviders = useMemo(() => {
     if (active?.harness === "claude" || active?.harness === "codex") {
       return [active.harness];