fix: resolve pre-commit formatting and missing UOM in stock balance test

- Reformat generator expression in add_alt_uom_columns to satisfy ruff
  line-length rule (pre-commit was auto-fixing this and failing CI)
- Create "Carton" UOM before use in test_alt_uom_balance_uses_first_alternate_uom
  to avoid LinkValidationError when "Carton" doesn't exist in test DB

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
(cherry picked from commit 987f606b4d)

erpnext/stock/report/stock_balance/stock_balance.py

@@ -614,7 +614,11 @@ class StockBalanceReport:
 			return
 
 		bal_qty_idx = next(
-			(i for i, col in enumerate(self.columns) if isinstance(col, dict) and col.get("fieldname") == "bal_qty"),
+			(
+				i
+				for i, col in enumerate(self.columns)
+				if isinstance(col, dict) and col.get("fieldname") == "bal_qty"
+			),
 			None,
 		)
 		if bal_qty_idx is None:

erpnext/stock/report/stock_balance/test_stock_balance.py

@@ -202,6 +202,7 @@ class TestStockBalance(ERPNextTestSuite):
 
 	def test_alt_uom_balance_uses_first_alternate_uom(self):
 		"""When an item has multiple alt UOMs, only the first (lowest idx) is shown."""
+		frappe.get_doc({"doctype": "UOM", "uom_name": "Carton"}).insert(ignore_if_duplicate=True)
 		self.item.append("uoms", {"conversion_factor": 12, "uom": "Box"})
 		self.item.append("uoms", {"conversion_factor": 144, "uom": "Carton"})
 		self.item.save()