test: massive coverage expansion — 15 new test modules + assistant tool fixes + orthogonal testing

- 10 translate plugin test files (100% coverage on 12 modules)
- assistant/handler tools: 85+ tests covering dispatch, registry, resolvers, routes, llm_planner, 13 tool handlers
- clean release: artifact_catalog_loader, mappers, approval, publication tests
- API routes: translate_helpers, validation_service extensions, datasets to 100%
- notifications: providers/service tests
- services: profile_preference_service
- docs/orthogonal-test-report.md — full speckit.tests audit
- Fixes: 3 git_base async mock failures, 4 assistant handler permission-check patches
- .gitignore: coverage artifacts

backend/tests/api/test_plugins.py

@@ -53,19 +53,25 @@ class TestListPlugins:
 
     def test_list_plugins_success(self):
         """Happy path: returns list of plugin configs."""
+        from src.core.plugin_base import PluginConfig
+
         mock_loader = MagicMock()
         mock_loader.get_all_plugin_configs.return_value = [
-            MagicMock(
+            PluginConfig(
+                id="superset-migration",
                 name="superset-migration",
                 version="1.0.0",
-                enabled=True,
                 description="Migration plugin",
+                ui_route="/plugins/migration",
+                schema={"type": "object", "properties": {}},
             ),
-            MagicMock(
+            PluginConfig(
+                id="superset-backup",
                 name="superset-backup",
                 version="2.0.0",
-                enabled=False,
                 description="Backup plugin",
+                ui_route="/plugins/backup",
+                schema={"type": "object", "properties": {}},
             ),
         ]