Keep Multimodal Leaderboard at top level with Document indented below

Hide the Multimodal section header and use CSS to indent Document
under Multimodal Leaderboard, matching the original sidebar hierarchy.

app.py

@@ -36,6 +36,16 @@ st.markdown("""
             border-left: 2px solid rgba(129, 150, 64, 0.3);
             margin-left: 0.75rem;
         }
+
+        /* Hide the Multimodal section header */
+        ul[data-testid="stSidebarNavItems"] > div:nth-child(4) > header {
+            display: none;
+        }
+
+        /* Indent Document under Multimodal Leaderboard */
+        ul[data-testid="stSidebarNavItems"] > div:nth-child(4) > li:nth-child(3) {
+            padding-left: 2rem;
+        }
     </style>
     """, unsafe_allow_html=True)