Disable executable code in Python docstrings

The exec="yes" flag in docstrings was causing build issues with
mkdocstrings + markdown-exec. The examples work fine when run
directly but fail during documentation generation. Disabling
execution for now to ensure clean builds.

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

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

Author: femtomc