docs(tools): add action-bound governance example

[jw-ond]

Summary

Adds a Python tools example showing how to bind a tool-side governance checkpoint to a canonical action hash before performing an external side effect.

The example is intentionally vendor-neutral and runs with an in-process checkpoint so it can be read and executed without any external service. A production deployment could replace the local checkpoint with an HTTP service that returns the same kind of decision object.

What it demonstrates

• Building a canonical action envelope from the proposed tool action
• Hashing that envelope before execution
• Calling a checkpoint before the side effect is performed
• Failing closed if the checkpoint decision is not bound to the same action hash
• Returning structured outcomes for approve, require_approval, and reject

Verification

PYTHONPATH=python /tmp/beeai-action-bound-venv/bin/python -m py_compile python/examples/tools/action_bound_governance.py
/tmp/beeai-action-bound-venv/bin/ruff check python/examples/tools/action_bound_governance.py python/examples/README.md
/tmp/beeai-action-bound-venv/bin/ruff format --check python/examples/tools/action_bound_governance.py
PYTHONPATH=python /tmp/beeai-action-bound-venv/bin/python python/examples/tools/action_bound_governance.py

The example prints one completed action, one approval-required action, and one rejected action.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.