[IMP] stock_picking_batch_custom: show product code as separate optional column

Add product_default_code related field to stock.move.line and
stock.picking.batch.summary.line. Show it as a hidden-by-default column
to the right of product_id in both detailed operations and product summary
views. Hide the code prefix from the product name via display_default_code
context so sorting is alphabetical.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

stock_picking_batch_custom/models/stock_move_line.py

@@ -17,6 +17,12 @@ class StockMoveLine(models.Model):
         readonly=True,
     )
 
+    product_default_code = fields.Char(
+        string="Product Code",
+        related="product_id.default_code",
+        readonly=True,
+    )
+
     is_collected = fields.Boolean(
         string="Collected",
         default=False,