fix: Improve AI auto-adjust prompt to prevent function wrapping

The AI was generating function definitions instead of inline code.
Updated the default prompt template to explicitly:
- Request inline executable code, NOT function definitions
- Clarify that variables are already available
- Emphasize no wrapping in functions

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

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

src/smarttools/ui_urwid.py

@@ -1829,7 +1829,9 @@ class SmartToolsUI:
         ai_provider_select_btn = Button3DCompact("▼", on_press=show_ai_provider_dropdown)
 
         # Default prompt template for AI code generation/adjustment
-        default_ai_prompt = f"""Modify or generate Python code according to my instruction below.
+        default_ai_prompt = f"""Write inline Python code (NOT a function definition) according to my instruction.
+
+The code runs directly - variables are already available, no function needed.
 
 INSTRUCTION: [Describe what you want]
 
@@ -1840,7 +1842,8 @@ CURRENT CODE:
 
 AVAILABLE VARIABLES: {', '.join(vars_available)}
 
-Return ONLY the Python code, no explanations or markdown fencing."""
+IMPORTANT: Return ONLY executable inline code. Do NOT wrap in a function.
+No explanations, no markdown fencing, just the code."""
 
         # Multiline editable prompt for AI with DOS-style scrollbar
         ai_prompt_edit = TabPassEdit(edit_text=default_ai_prompt, multiline=True)