feat(configurator): auto-load latest part description version on order entry

Wizard line (direct + express) and SO line now pre-fill BOTH internal +
customer-facing from the part's latest version (fallback to
default_specification_text), without clobbering typed text.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

fusion_plating/fusion_plating_configurator/tests/test_part_description_history.py

@@ -72,3 +72,13 @@ class TestPartDescriptionHistory(TransactionCase):
             [('part_catalog_id', '=', self.part.id)])
         self.assertEqual(len(versions), 2)
         self.assertEqual(self.part.default_specification_text, 'c2')
+
+    # ----- Task 5: SO line auto-load -----
+    def test_so_line_onchange_loads_latest_version(self):
+        self.part._fp_save_description_version('shop notes', 'cust spec')
+        line = self.env['sale.order.line'].new({
+            'x_fc_part_catalog_id': self.part.id,
+        })
+        line._fp_onchange_part_load_description()
+        self.assertEqual(line.name, 'cust spec')
+        self.assertEqual(line.x_fc_internal_description, 'shop notes')