test(phase2): add unit tests for core, persistence, plugin, utils

- Add test_handler_helpers.py for plugin handler helpers (7 tests)
- Add test_mgr_methods.py for persistence manager (5 tests)
- Add test_app_config_validation.py for core app config (12 tests)
- Add test_knowledge_service.py for API knowledge service (22 tests)
- Add test_kbmgr.py for RAG knowledge base manager (39 tests)
- Add test_survey_manager.py for survey manager (22 tests)
- Add test_connector_methods.py for plugin connector (24 tests)
- Add test_funcschema.py for utils function schema (9 tests)
- Add test_platform.py for utils platform detection (7 tests)
- Add test_extract_deps.py for plugin deps extraction (7 tests)
- Add test_database_decorator.py for persistence decorator (7 tests)
- Add test_load_config.py for core config loading (19 tests)
- Add COVERAGE_EXCLUSIONS.md documenting external adapter exclusions
- Fix test_chat_session_limit.py path for portability

Coverage: core 28% → 30%, persistence 24% → 24.4%, plugin 27% → 28%
Total: 1082 tests passed, core module coverage 45.5%

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

tests/unit_tests/pipeline/test_chat_session_limit.py

@@ -91,7 +91,11 @@ async def test_preprocessor_keeps_conversation_when_last_update_is_not_expired(m
 
 
 def test_expire_time_metadata_lives_under_ai_runner_not_safety():
-    metadata_dir = Path('src/langbot/templates/metadata/pipeline')
+    # Use path relative to test file location for portability
+    # test file: tests/unit_tests/pipeline/test_chat_session_limit.py
+    # project root: 4 levels up
+    project_root = Path(__file__).parent.parent.parent.parent
+    metadata_dir = project_root / 'src' / 'langbot' / 'templates' / 'metadata' / 'pipeline'
 
     ai_meta = yaml.safe_load((metadata_dir / 'ai.yaml').read_text())
     safety_meta = yaml.safe_load((metadata_dir / 'safety.yaml').read_text())