leaderboard: fix tasks iframe fit (use body.scrollHeight)

documentElement.scrollHeight floors at the iframe viewport height, so the
previous fit never shrank a short detail card below the 90vh fallback (the
blank gap persisted). body.scrollHeight reflects the real content height;
verified the iframe now matches content on both desktop and mobile.

Co-authored-by: Cursor <cursoragent@cursor.com>

tasks.py

@@ -510,7 +510,10 @@ let query = '', typeFilter = 'all';
 function fitFrame() {
   try {
     const fe = window.frameElement;
-    if (fe) fe.style.height = Math.ceil(document.documentElement.scrollHeight) + 'px';
+    // body.scrollHeight (not documentElement's) reflects the real content
+    // height; documentElement.scrollHeight floors at the iframe viewport, so
+    // it would never shrink a short detail card below the fallback height.
+    if (fe) fe.style.height = Math.ceil(document.body.scrollHeight) + 'px';
   } catch (e) { /* sandboxed -> keep fallback height */ }
 }