Change "Rename Multiple Speakers" to "Rename Cross-file Speakers"

ui.py

@@ -131,7 +131,7 @@ def render_rename_sidebar(currFile, speakerNames, display_speaker_tokens, token_
     raw_to_display = {v: k for k, v in token_display_map.items()}
 
     st.sidebar.divider()
-    st.sidebar.subheader("Rename Multiple Speakers")
+    st.sidebar.subheader("Rename Cross-file Speakers")
     st.sidebar.markdown(
         "<p style='font-size:0.85rem; color:gray; margin-bottom:2px;'>"
         "This option works best for renaming multiple speakers across multiple files. "