Mock code executor returns misleading success response

[lukeinglis]

Problem

demo_ui/backend/tools.py:359 mock code executor returns fake "execution completed successfully" which could mislead blog readers about security posture.

Fix

Change response to clearly indicate demo mode: "Code execution disabled in demo".

Priority

Important

🤖 Generated with Claude Code

[lukeinglis]

Closing: these were filed against the ITS demo by mistake, not the its_hub library.