docs: add asqav audit trail cookbook using InterventionHandler

[jagmarques]

Summary

• Adds a cookbook recipe showing how to use asqav with DefaultInterventionHandler to create a tamper-evident audit trail for agent messages and tool calls.
• The recipe subclasses DefaultInterventionHandler to intercept on_send, on_publish, and on_response hooks, signing each action to asqav's ML-DSA (FIPS 204) audit log.
• Adds the new recipe to the cookbook index.

Details

asqav is an open-source Python SDK (pip install asqav) that provides cryptographically signed audit trails for AI agents. The integration is lightweight - a single AsqavInterventionHandler class that plugs into SingleThreadedAgentRuntime.

The cookbook covers:

• Creating an AsqavInterventionHandler that logs sends, publishes, responses, and tool calls
• Wiring it into the runtime via intervention_handlers
• What gets logged at each lifecycle hook

Test plan

• Verify notebook renders correctly in the docs build
• Confirm cookbook index includes the new entry

[jagmarques]

@microsoft-github-policy-service agree

[jagmarques]

Just checking if this is ready for review. Happy to address any feedback.