The DataGrid emits @sort events when column headers are clicked, but
MongoDocBrowser was not listening to them. Added an onSort handler that
converts the column/direction into MongoDB sort JSON format.
- frontend: use e.message instead of String(e) in toErrorResult to avoid
"Error: " prefix for HTTP-mode errors, matching connectionErrorMessage
- frontend: apply same fix to MongoDocBrowser error display
- backend(postgres): use pg_error_to_string across all query execution
paths (execute, execute_batch, copy_out, copy_in) to extract DbError
details instead of generic transport-layer errors
Other databases (MySQL, SQL Server, SQLite, DuckDB) already include
server-level error details in their native Error::to_string().
t8y2