test(fusion_accounting_reports): coexistence behavior

Mirrors Phase 1's coexistence test pattern. Verifies:

- The coexistence group (group_fusion_show_when_enterprise_absent)
  exists and is referenceable
- The reports engine model (fusion.report.engine) is always
  registered, regardless of Enterprise install state
- The Financial Reports root menu requires the coexistence group
- The Open Report... sub-menu (period picker wizard) is gated too

Uses V19 group_ids attribute with a graceful fallback to groups_id for
older runtime variants.

Tests: 3 new (test_coexistence.py). Net 115 -> 118.
Made-with: Cursor

fusion_accounting_reports/__manifest__.py

@@ -1,6 +1,6 @@
 {
     'name': 'Fusion Accounting Reports',
-    'version': '19.0.1.0.34',
+    'version': '19.0.1.0.35',
     'category': 'Accounting/Accounting',
     'summary': 'AI-augmented financial reports (P&L, balance sheet, trial balance, GL).',
     'description': """

fusion_accounting_reports/tests/__init__.py

@@ -22,3 +22,4 @@ from . import test_pdf_export
 from . import test_xlsx_export
 from . import test_period_picker
 from . import test_migration_round_trip
+from . import test_coexistence

fusion_accounting_reports/tests/test_coexistence.py

@@ -0,0 +1,39 @@
+"""Coexistence tests for fusion_accounting_reports.
+
+Mirrors Phase 1's coexistence test pattern: verifies the menu requires
+the coexistence group, and the engine model is always available."""
+
+from odoo.tests.common import TransactionCase, tagged
+
+
+@tagged('post_install', '-at_install')
+class TestReportsCoexistence(TransactionCase):
+
+    def setUp(self):
+        super().setUp()
+        self.coex_group = self.env.ref(
+            'fusion_accounting_core.group_fusion_show_when_enterprise_absent',
+            raise_if_not_found=False,
+        )
+        self.assertIsNotNone(self.coex_group, "Coexistence group must exist")
+
+    def test_engine_always_available(self):
+        """The engine is registered regardless of Enterprise install state."""
+        self.assertIn('fusion.report.engine', self.env.registry)
+
+    def test_menu_gated_by_coexistence_group(self):
+        menu = self.env.ref('fusion_accounting_reports.menu_fusion_reports_root',
+                            raise_if_not_found=False)
+        if not menu:
+            self.skipTest("Menu not loaded")
+        menu_groups = getattr(menu, 'group_ids', None) or menu.groups_id
+        self.assertIn(self.coex_group, menu_groups,
+                      "Reports root menu must require the coexistence group")
+
+    def test_period_picker_wizard_gated_too(self):
+        menu = self.env.ref('fusion_accounting_reports.menu_fusion_reports_open',
+                            raise_if_not_found=False)
+        if not menu:
+            self.skipTest("Menu not loaded")
+        menu_groups = getattr(menu, 'group_ids', None) or menu.groups_id
+        self.assertIn(self.coex_group, menu_groups)