Add error boundary around object viewers

Wrap the resolved viewer in an error boundary so a render failure (e.g.
WebGL context loss or a model/texture load error) is contained to the
inspector pane instead of crashing the page. The fallback shows the
error message and stack trace.

apps/web/src/components/ErrorBoundary.tsx

@@ -0,0 +1,54 @@
+import { Component, type ErrorInfo, type ReactNode } from 'react';
+
+interface Props {
+  children: ReactNode;
+  /** Optional fallback rendered in place of `children` when an error is caught. */
+  fallback?: (error: Error) => ReactNode;
+}
+
+interface State {
+  error: Error | null;
+}
+
+/**
+ * Catches render errors in its subtree and renders a fallback instead of
+ * letting them crash the whole page. Used to isolate failures in object
+ * viewers (e.g. WebGL context loss, model/texture load errors).
+ */
+export default class ErrorBoundary extends Component<Props, State> {
+  override state: State = { error: null };
+
+  static getDerivedStateFromError(error: Error): State {
+    return { error };
+  }
+
+  override componentDidCatch(error: Error, info: ErrorInfo) {
+    // Surface the error for debugging without breaking the UI.
+    console.error('Viewer error:', error, info.componentStack);
+  }
+
+  override render() {
+    if (this.state.error) {
+      return this.props.fallback
+        ? this.props.fallback(this.state.error)
+        : <DefaultFallback error={this.state.error} />;
+    }
+    return this.props.children;
+  }
+}
+
+function DefaultFallback({ error }: { error: Error }) {
+  return (
+    <div className="flex h-80 flex-col items-center justify-center gap-2 overflow-auto rounded-lg border border-zinc-800 bg-zinc-900 p-4 text-center">
+      <p className="text-sm font-medium text-zinc-200">Couldn't render this object</p>
+      <p className="max-w-sm wrap-break-word font-mono text-xs text-zinc-400">
+        {error.message}
+      </p>
+      {error.stack && (
+        <pre className="mt-2 max-h-40 w-full overflow-auto whitespace-pre-wrap text-left font-mono text-[10px] leading-relaxed text-zinc-600">
+          {error.stack}
+        </pre>
+      )}
+    </div>
+  );
+}

apps/web/src/pages/ModPage.tsx

@@ -6,6 +6,7 @@ import { useModStore } from '../stores/modStore';
 import { useSearchStore } from '../stores/searchStore';
 import { modFileUrl } from '../api';
 import ObjectTree from '../components/ObjectTree';
+import ErrorBoundary from '../components/ErrorBoundary';
 import { resolveViewer } from '../components/viewers';
 import { iconsForObject } from '../components/objectIcons';
 // Register the 3D viewers (side effect) so `resolveViewer` can find them.
@@ -78,15 +79,17 @@ export default function ModPage() {
                 </p>
               </header>
               {Viewer && (
-                <Suspense
+                <ErrorBoundary>
-                  fallback={
+                  <Suspense
-                    <div className="flex h-80 items-center justify-center text-sm text-zinc-500">
+                    fallback={
-                      Loading viewer…
+                      <div className="flex h-80 items-center justify-center text-sm text-zinc-500">
-                    </div>
+                        Loading viewer…
-                  }
+                      </div>
-                >
+                    }
-                  <Viewer object={selected.object} />
+                  >
-                </Suspense>
+                    <Viewer object={selected.object} />
+                  </Suspense>
+                </ErrorBoundary>
               )}
             </>
           ) : (