Don't operate on 'Agent' column until we know it's present (#9)

.gitignore

@@ -179,3 +179,4 @@ cython_debug/
 .DS_Store
 .mise.toml
 .vscode/
+.gradio/

leaderboard_transformer.py

@@ -204,12 +204,13 @@ class DataTransformer:
             df_sorted = self.data.sort_values(primary_score_col, ascending=False, na_position='last')
 
         df_view = df_sorted.copy()
-        #preserve just agent name for scatterplot hover
-        df_view['agent_for_hover'] = df_view['Agent']
+
         # 3. Combine "Agent" and "Submitter" into a single HTML-formatted column
         #    We do this *before* defining the final column list.
         if 'Agent' in df_view.columns and 'Submitter' in df_view.columns:
-
+            #preserve just agent name for scatterplot hover
+            df_view['agent_for_hover'] = df_view['Agent']
+            
             def combine_agent_submitter(row):
                 agent = row['Agent']
                 submitter = row['Submitter']