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/utils/test_platform.py

@@ -0,0 +1,89 @@
+"""Unit tests for utils platform detection.
+
+Tests cover:
+- get_platform() function
+- Docker environment detection
+- WebSocket plugin runtime mode
+"""
+from __future__ import annotations
+
+import os
+import sys
+from unittest.mock import patch
+from importlib import import_module
+
+
+def get_platform_module():
+    """Lazy import to avoid circular import issues."""
+    return import_module('langbot.pkg.utils.platform')
+
+
+class TestGetPlatform:
+    """Tests for get_platform function."""
+
+    def test_returns_docker_when_dockerenv_exists(self):
+        """Test returns 'docker' when /.dockerenv file exists."""
+        platform_module = get_platform_module()
+
+        with patch('os.path.exists', return_value=True):
+            with patch.dict(os.environ, {}, clear=True):
+                result = platform_module.get_platform()
+                assert result == 'docker'
+
+    def test_returns_docker_when_env_var_true(self):
+        """Test returns 'docker' when DOCKER_ENV=true."""
+        platform_module = get_platform_module()
+
+        with patch('os.path.exists', return_value=False):
+            with patch.dict(os.environ, {'DOCKER_ENV': 'true'}, clear=True):
+                result = platform_module.get_platform()
+                assert result == 'docker'
+
+    def test_returns_sys_platform_when_not_docker(self):
+        """Test returns sys.platform when not in Docker."""
+        platform_module = get_platform_module()
+
+        with patch('os.path.exists', return_value=False):
+            with patch.dict(os.environ, {'DOCKER_ENV': 'false'}, clear=True):
+                result = platform_module.get_platform()
+                assert result == sys.platform
+
+    def test_returns_sys_platform_when_no_env_var(self):
+        """Test returns sys.platform when DOCKER_ENV not set."""
+        platform_module = get_platform_module()
+
+        with patch('os.path.exists', return_value=False):
+            # Make sure DOCKER_ENV is not set
+            env_copy = os.environ.copy()
+            if 'DOCKER_ENV' in env_copy:
+                del env_copy['DOCKER_ENV']
+            with patch.dict(os.environ, env_copy, clear=True):
+                result = platform_module.get_platform()
+                assert result == sys.platform
+
+    def test_standalone_runtime_default_false(self):
+        """Test standalone_runtime defaults to False."""
+        platform_module = get_platform_module()
+
+        # Check the module attribute
+        assert platform_module.standalone_runtime is False
+
+    def test_use_websocket_returns_standalone_runtime(self):
+        """Test use_websocket_to_connect_plugin_runtime returns standalone_runtime."""
+        platform_module = get_platform_module()
+
+        result = platform_module.use_websocket_to_connect_plugin_runtime()
+        assert result == platform_module.standalone_runtime
+
+    def test_standalone_runtime_can_be_modified(self):
+        """Test standalone_runtime can be modified."""
+        platform_module = get_platform_module()
+
+        original = platform_module.standalone_runtime
+
+        # Modify
+        platform_module.standalone_runtime = True
+        assert platform_module.use_websocket_to_connect_plugin_runtime() is True
+
+        # Restore
+        platform_module.standalone_runtime = original