SIGSEGV crash in CursorWrap::close during rapid drop_table + drop_schema sequence

## Problem

Executing `drop_table` and `drop_schema` in rapid succession (no delay between the two) causes a segmentation fault inside `CursorWrap::close` in the LMDB native module.

```
PID 2178 received SIGSEGV for address: 0xc
3 node.napi.node CursorWrap::close
4 node.napi.node InstanceMethodCallbackWrapper
```

Adding a timeout between the two operations prevents the crash, suggesting the cursor from the dropped table is still being held when the schema drop attempts to close it.

🤖 Filed by Claude on behalf of Kris.