fix: emit bracketed inline array syntax for scalar subquery expressions (#17716)

Fixes a SQLGlot transpilation bug in BigQuery array generation where
single-element arrays containing scalar subqueries wrapped in
expressions (e.g., `COALESCE(CAST(...))` or `ROUND(...)`) produced
invalid BigQuery SQL syntax `ARRAY(COALESCE(...))`, causing BigQuery
`400 Syntax error: Unexpected identifier "COALESCE"` errors on
`.cache()`.

Verified at:
before: screen/9AmutJHVDJuafwm
after: screen/u7aW9tTLB8ybUFW

Fixes #<534824500> 🦕

Author: shuoweil

packages/bigframes/tests/unit/core/compile/sqlglot/expressions/snapshots/test_array_ops/test_to_array_with_subquery_expression/out.sql

@@ -0,0 +1,12 @@
+SELECT
+  [
+    COALESCE(
+      (
+        SELECT
+          COALESCE(SUM(bf_arr_reduce_uid), 0)
+        FROM UNNEST(`float_list_col`) AS bf_arr_reduce_uid
+      ),
+      0.0
+    )
+  ] AS `arr_subquery_coalesce`
+FROM `bigframes-dev`.`sqlglot_test`.`repeated_types` AS `bft_0`

packages/bigframes/tests/unit/core/compile/sqlglot/expressions/test_array_ops.py

@@ -104,3 +104,14 @@ def test_to_array_op(scalar_types_df: bpd.DataFrame, snapshot):
 
     sql = utils._apply_ops_to_sql(bf_df, list(ops_map.values()), list(ops_map.keys()))
     snapshot.assert_match(sql, "out.sql")
+
+
+def test_to_array_with_subquery_expression(repeated_types_df: bpd.DataFrame, snapshot):
+    reduced = ops.ArrayReduceOp(agg_ops.SumOp()).as_expr("float_list_col")
+    coalesced_reduced = ops.coalesce_op.as_expr(reduced, expression.const(0.0))
+    array_expr = ops.ToArrayOp().as_expr(coalesced_reduced)
+
+    sql = utils._apply_ops_to_sql(
+        repeated_types_df, [array_expr], ["arr_subquery_coalesce"]
+    )
+    snapshot.assert_match(sql, "out.sql")

packages/bigframes/third_party/bigframes_vendored/sqlglot/dialects/dialect.py

@@ -1236,7 +1236,14 @@ def inline_array_sql(self: Generator, expression: exp.Expression) -> str:
 
 def inline_array_unless_query(self: Generator, expression: exp.Expression) -> str:
     elem = seq_get(expression.expressions, 0)
-    if isinstance(elem, exp.Expression) and elem.find(exp.Query):
+    if (
+        len(expression.expressions) == 1
+        and isinstance(elem, exp.Expression)
+        and (
+            isinstance(elem, exp.Query)
+            or (isinstance(elem, exp.Subquery) and isinstance(elem.this, exp.Query))
+        )
+    ):
         return self.func("ARRAY", elem)
     return inline_array_sql(self, expression)