[IMP] stock_picking_batch_custom: order detailed ops by category, product, partner

Store picking_partner_id on stock.move.line and set default_order to
product_categ_id, product_id, picking_partner_id in the detailed operations view.

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

stock_picking_batch_custom/models/stock_move_line.py

@@ -23,6 +23,12 @@ class StockMoveLine(models.Model):
         readonly=True,
     )
 
+    picking_partner_id = fields.Many2one(
+        related="picking_id.partner_id",
+        store=True,
+        readonly=True,
+    )
+
     is_collected = fields.Boolean(
         string="Collected",
         default=False,

stock_picking_batch_custom/views/stock_picking_batch_views.xml

@@ -46,6 +46,9 @@
         <field name="model">stock.move.line</field>
         <field name="inherit_id" ref="stock_picking_batch.view_move_line_tree"/>
         <field name="arch" type="xml">
+            <xpath expr="//list" position="attributes">
+                <attribute name="default_order">product_categ_id,product_id,picking_partner_id</attribute>
+            </xpath>
             <xpath expr="//field[@name='product_id']" position="before">
                 <field name="product_categ_id" readonly="1"/>
             </xpath>