Add cursor pointer and click-outside-to-dismiss to model selector modal

- Add cursor-pointer class to X button in ModelSelectionModal
- Add onClick handler to backdrop overlay to close modal
- Add stopPropagation to modal content to prevent backdrop clicks
- Consistent modal behavior between model selector and MCP server modals

examples/chat-ui/src/components/ModelSelectionModal.tsx

@@ -86,13 +86,19 @@ const ModelSelectionModal: React.FC<ModelSelectionModalProps> = ({
 
   return (
     <>
-      <div className="fixed inset-0 bg-black bg-opacity-50 z-50 flex items-center justify-center p-4">
-        <div className="bg-white rounded-lg shadow-xl w-full max-w-2xl max-h-[80vh] overflow-hidden">
+      <div 
+        className="fixed inset-0 bg-black bg-opacity-50 z-50 flex items-center justify-center p-4"
+        onClick={onClose}
+      >
+        <div 
+          className="bg-white rounded-lg shadow-xl w-full max-w-2xl max-h-[80vh] overflow-hidden"
+          onClick={(e) => e.stopPropagation()}
+        >
           <div className="flex items-center justify-between p-6 border-b border-zinc-200">
             <h2 className="text-xl font-semibold text-zinc-900">Select Model</h2>
             <button
               onClick={onClose}
-              className="text-zinc-400 hover:text-zinc-600 p-1"
+              className="text-zinc-400 hover:text-zinc-600 p-1 cursor-pointer"
             >
               <X size={24} />
             </button>