fix: initialize activeModel to null so first switchModel actually loads

index.html

@@ -427,7 +427,7 @@
   const toggleDistilbert = document.getElementById('toggle-distilbert');
   const toggleHrm = document.getElementById('toggle-hrm');
 
-  let activeModel = 'distilbert';
+  let activeModel = null;
   let distilbertClassifier = null;
   let hrmSession = null;
   let isLoading = false;