Add DOS scrollbar to AI prompt editor

Wrap the AI prompt ListBox in DOSScrollBar for consistent
scrolling experience in the auto-adjust panel.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

src/smarttools/ui_urwid.py

@@ -1646,12 +1646,13 @@ AVAILABLE VARIABLES: {', '.join(vars_available)}
 
 Return ONLY the Python code, no explanations or markdown fencing."""
 
-        # Multiline editable prompt for AI
+        # Multiline editable prompt for AI with DOS-style scrollbar
         ai_prompt_edit = TabPassEdit(edit_text=default_ai_prompt, multiline=True)
         ai_prompt_styled = urwid.AttrMap(ai_prompt_edit, 'edit', 'edit_focus')
         ai_prompt_walker = urwid.SimpleFocusListWalker([ai_prompt_styled])
         ai_prompt_listbox = urwid.ListBox(ai_prompt_walker)
-        ai_prompt_box = urwid.LineBox(ai_prompt_listbox, title="Prompt")
+        ai_prompt_scrollbar = DOSScrollBar(ai_prompt_listbox)
+        ai_prompt_box = urwid.LineBox(ai_prompt_scrollbar, title="Prompt")
 
         # Output/feedback area for AI responses
         ai_output_text = urwid.Text("")