Extension Ecosystem Example

This example demonstrates phase 7 extension points:

route.resolve/v1 returns override, reject, or pass.
status.ping/v1 returns host-specific MOTD text.
event.subscriber/v1 receives asynchronous plugin events.
admin.auth.provider/v1 registers an unavailable external provider while preserving local admin fallback.

It is intended as a conformance fixture and source example for plugin authors.