fix(inspect-ui): correct HierarchyPanel CSS variable names

Tokens --surface-1/--surface-2/--text-secondary/--border-subtle don't
exist in tokens.css, so sticky thead had no background and tag/bounds
text fell back to inherited color. Map to the canonical --surface,
--surface-elevated, --text-muted, --border that other panels use.

inspect-ui/dist/index.html

@@ -4,8 +4,8 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>sanderling inspect</title>
-    <script type="module" crossorigin src="/assets/index-jfR9BOx8.js"></script>
-    <link rel="stylesheet" crossorigin href="/assets/index-t-0uLX7u.css">
+    <script type="module" crossorigin src="/assets/index-CEStFXHZ.js"></script>
+    <link rel="stylesheet" crossorigin href="/assets/index-BV6z-_9-.css">
   </head>
   <body>
     <div id="root"></div>