New module kindred_sdk/events.py provides lightweight publish-subscribe
so addons can signal each other without direct imports.
New public API:
- sdk.on(event, handler) — subscribe to a named event
- sdk.off(event, handler) — unsubscribe
- sdk.emit(event, data) — publish event with dict payload
Pure Python, synchronous dispatch, snapshot-safe iteration.
Handlers that raise are logged and skipped without breaking the chain.
