Division by a compound expression loses its parentheses on Snowflake and Databricks #439

When a definition divides by a compound expression, the SQL for Snowflake and Databricks drops the parentheses around the divisor. The DuckDB SQL is correct.

The first query runs and returns a wrong value, with no error. The second fails with Division by zero when ratio is 0, because the zero check tests ratio + 1.0 but the query divides by ratio.

Both packages have the same fault: _divide() and definition_sql_divide() render both operands at the lowest precedence, then join them with /. definition-warehouse-sql.json has no case with a compound divisor, so neither suite finds this without a live warehouse. Found by test_the_emitted_definition_sql_agrees_with_duckdb in #434.