Make adapter.after_update optionally async

Allow and mange both signatures
```python
def after_update(self) -> None:
...

async def after_update(self) -> None:
...
```

Locate the adapter.after_update hook and inspect how update callbacks are invoked. Trace the existing synchronous path, then verify that both regular and async after_update implementations are supported and covered by the relevant tests.

Written by the indexing model from the issue text.