Fix MotherDuck segfault when switching from other database connections

Disable process worker for MotherDuck to avoid segfault that occurs when
the subprocess has already loaded other database drivers before loading
the DuckDB/MotherDuck native library.

MotherDuck queries now run in the main process like local DuckDB.

Author: Maxteabag

sqlit/domains/connections/providers/motherduck/adapter.py

@@ -20,8 +20,13 @@ def name(self) -> str:
 
     @property
     def supports_process_worker(self) -> bool:
-        """MotherDuck handles concurrency server-side."""
-        return True
+        """Disable process worker to avoid segfault when switching from other DBs.
+
+        The MotherDuck/DuckDB native library has issues when loaded in a subprocess
+        that has already loaded other database drivers. Running in the main process
+        avoids this issue.
+        """
+        return False
 
     @property
     def supports_multiple_databases(self) -> bool: