Add Hugging Face user ID support for automatic persona assignment

app.py

@@ -354,14 +354,25 @@ with st.sidebar:
     set_model(model_id)
 
     st.markdown("#### Choose user persona")
+    
+    # Get Hugging Face user ID if available (in HF Spaces)
+    hf_user_id = os.getenv("SPACE_USER") or os.getenv("HF_USERNAME")
+    
+    if hf_user_id:
+        # Use HF user ID as default, but allow override
+        st.info(f"👤 Signed in as: **{hf_user_id}**")
+        default_persona = hf_user_id
+    else:
+        default_persona = "Charlie"
+    
     selected_persona = st.selectbox(
         "Choose user persona",
         ["Charlie", "Jing", "Charles", "Control"],
         label_visibility="collapsed",
     )
-    custom_persona = st.text_input("Or enter your name", "")
+    custom_persona = st.text_input("Or enter your name", default_persona if hf_user_id else "")
     persona_name = (
-        custom_persona.strip() if custom_persona.strip() else selected_persona
+        custom_persona.strip() if custom_persona.strip() else (hf_user_id if hf_user_id else selected_persona)
     )
 
     compare_personas = st.checkbox("Compare with Control persona")