Returns the audit sources available in your environment and the event types
each has emitted. Use this to populate filter options for the filter endpoint.

The response always includes these known sources (in order):

• api-gateway — Request context (actor, method, path) for audited operations
• blueprints — Blueprint lifecycle events (create, update, archive)
• ai-policy — AI policy evaluation and enforcement events

Gateway events capture who made a request; service events (blueprints, ai-policy)
capture what changed. They share a transaction id, so you can trace an actor
to the resources they affected.

Each source reports hasEvents: true if your environment has events from it
in the time window, along with the distinct types seen. Additional sources
may appear if your environment has events from them.

Required Permissions: read:env:audit (environment scope) or read:org:audit (organization scope)