feat(web): make object tree collapsible and collapsed by default

apps/web/src/components/ObjectTree.tsx

@@ -1,3 +1,4 @@
+import { useState } from 'react';
 import type { ObjectTreeNode } from '@tts/extract';
 
 interface Props {
@@ -38,23 +39,44 @@ function TreeNode({
   onSelect: (guid: string) => void;
 }) {
   const selected = node.object.GUID === selectedGuid;
+  const hasChildren = node.children.length > 0;
+  const [expanded, setExpanded] = useState(false);
   return (
     <li>
-      <button
+      <div
-        onClick={() => onSelect(node.object.GUID)}
+        className={`flex items-center rounded pr-2 ${
-        style={{ paddingLeft: `${depth * 16 + 8}px` }}
-        className={`block w-full truncate rounded px-2 py-1 text-left text-sm ${
           selected
             ? 'bg-zinc-700 text-zinc-100'
             : 'text-zinc-300 hover:bg-zinc-800 hover:text-zinc-100'
         }`}
+        style={{ paddingLeft: `${depth * 16 + 4}px` }}
+      >
+        {hasChildren ? (
+          <button
+            onClick={() => setExpanded((e) => !e)}
+            aria-label={expanded ? 'Collapse' : 'Expand'}
+            className="flex h-6 w-6 shrink-0 items-center justify-center rounded text-zinc-500 hover:text-zinc-200"
+          >
+            <span
+              className={`inline-block text-xs transition-transform ${expanded ? 'rotate-90' : ''}`}
+            >
+              ▸
+            </span>
+          </button>
+        ) : (
+          <span className="h-6 w-6 shrink-0" />
+        )}
+        <button
+          onClick={() => onSelect(node.object.GUID)}
+          className="block min-w-0 flex-1 truncate py-1 text-left text-sm"
         >
           <span className="mr-1.5 rounded bg-zinc-800 px-1 py-0.5 text-xs uppercase text-zinc-500">
             {node.object.Name}
           </span>
           <span className="truncate">{node.label}</span>
         </button>
-      {node.children.length > 0 && (
+      </div>
+      {hasChildren && expanded && (
         <ul>
           {node.children.map((child, index) => (
             <TreeNode