fix: define hide_welcome before Custom vertical validation check

NameError caused Gradio Error badge when GO pressed with Custom
vertical and empty Context field.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

chat_interface.py

@@ -5204,6 +5204,7 @@ def create_chat_tab(chat_controller_state, settings, current_stage, current_mode
                 raw_company = f"{vertical} Demo"
 
             is_custom = (vertical == "Custom")
+            hide_welcome = gr.update(visible=False)
 
             if is_custom:
                 # Custom vertical: context IS the use case; function dropdown is ignored
@@ -5240,7 +5241,6 @@ def create_chat_tab(chat_controller_state, settings, current_stage, current_mode
 
             # Drive straight to awaiting_context → 'proceed' to skip confirmation dialog
             history = history or []
-            hide_welcome = gr.update(visible=False)
             try:
                 for result in controller.process_chat_message(
                     "proceed", history, 'awaiting_context', model,