fix: prevent DOM error when removing temporary download link (#675) (#676)

Add defensive checks before removeChild to prevent 'Failed to execute removeChild' error when the element has already been removed from DOM. Wrap URL.revokeObjectURL in finally block to ensure proper resource cleanup.

web/src/app/chat/components/research-block.tsx

@@ -87,8 +87,13 @@ export function ResearchBlock({
     document.body.appendChild(a);
     a.click();
     setTimeout(() => {
-      document.body.removeChild(a);
-      URL.revokeObjectURL(url);
+      try {
+        if (a.parentNode) {
+          a.parentNode.removeChild(a);
+        }
+      } finally {
+        URL.revokeObjectURL(url);
+      }
     }, 0);
   }, [reportId]);