feat(configurator): per-part description version model + part load/save helpers

fp.part.description.version: immutable per-part snapshots with version_no/
is_latest maintained in create(), titled "<SO#> · <date>". fp.part.catalog
gains description_version_ids + _fp_resolve_line_descriptions (load latest,
fallback to default_specification_text) and _fp_save_description_version
(dedup + sync default). ACL mirrors fp.sale.description.template.

Tests deferred to entech (local Docker unavailable this session).

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

fusion_plating/fusion_plating_configurator/tests/__init__.py

@@ -7,3 +7,4 @@ from . import test_express_line_fields
 from . import test_express_so_line_fields
 from . import test_express_sale_order_fields
 from . import test_express_wizard_fields
+from . import test_part_description_history

fusion_plating/fusion_plating_configurator/tests/test_part_description_history.py

@@ -0,0 +1,74 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+"""Per-part description history (spec 2026-05-29)."""
+from odoo.tests.common import TransactionCase, tagged
+
+
+@tagged('post_install', '-at_install', 'fp_desc_history')
+class TestPartDescriptionHistory(TransactionCase):
+
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        cls.partner = cls.env['res.partner'].create({'name': 'DescCust'})
+        cls.part = cls.env['fp.part.catalog'].create({
+            'partner_id': cls.partner.id,
+            'part_number': 'DH-001',
+            'revision': 'A',
+            'name': 'Desc Part',
+        })
+
+    def _mk_version(self, internal, customer, **kw):
+        vals = {
+            'part_catalog_id': self.part.id,
+            'internal_description': internal,
+            'customer_facing_description': customer,
+        }
+        vals.update(kw)
+        return self.env['fp.part.description.version'].create(vals)
+
+    # ----- Task 1: model invariants -----
+    def test_version_no_increments_and_is_latest_flips(self):
+        v1 = self._mk_version('int 1', 'cust 1')
+        v2 = self._mk_version('int 2', 'cust 2')
+        self.assertEqual(v1.version_no, 1)
+        self.assertEqual(v2.version_no, 2)
+        self.assertFalse(v1.is_latest)
+        self.assertTrue(v2.is_latest)
+
+    def test_name_uses_order_and_date(self):
+        so = self.env['sale.order'].create({'partner_id': self.partner.id})
+        v = self._mk_version('i', 'c', sale_order_id=so.id,
+                             source_date='2026-05-29')
+        self.assertIn(so.name, v.name)
+        self.assertIn('2026-05-29', v.name)
+
+    # ----- Task 2: part helpers -----
+    def test_resolve_falls_back_to_default_spec(self):
+        self.part.default_specification_text = 'legacy cust'
+        descs = self.part._fp_resolve_line_descriptions()
+        self.assertEqual(descs['customer_facing'], 'legacy cust')
+        self.assertEqual(descs['internal'], '')
+
+    def test_resolve_prefers_latest_version(self):
+        self.part.default_specification_text = 'legacy cust'
+        self._mk_version('hist int', 'hist cust')
+        descs = self.part._fp_resolve_line_descriptions()
+        self.assertEqual(descs['customer_facing'], 'hist cust')
+        self.assertEqual(descs['internal'], 'hist int')
+
+    def test_save_dedups_when_unchanged(self):
+        self.part._fp_save_description_version('i', 'c')
+        self.part._fp_save_description_version('i', 'c')  # identical
+        self.assertEqual(
+            self.env['fp.part.description.version'].search_count(
+                [('part_catalog_id', '=', self.part.id)]), 1)
+
+    def test_save_creates_new_on_change_and_syncs_default(self):
+        self.part._fp_save_description_version('i1', 'c1')
+        self.part._fp_save_description_version('i1', 'c2')  # changed
+        versions = self.env['fp.part.description.version'].search(
+            [('part_catalog_id', '=', self.part.id)])
+        self.assertEqual(len(versions), 2)
+        self.assertEqual(self.part.default_specification_text, 'c2')