test(e2e): add minimal startup E2E tests

Add E2E tests for LangBot startup flow:
- tests/e2e/utils/config_factory.py: minimal config generation
- tests/e2e/utils/process_manager.py: LangBot subprocess management
- tests/e2e/conftest.py: E2E fixtures (session-scoped process)
- tests/e2e/test_startup.py: 12 tests for startup verification

Tests verify:
- boot.py + stages execution
- database initialization (SQLite)
- API availability
- migrations applied

Uses embedded databases (SQLite, Chroma) - no external dependencies.

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

pytest.ini

@@ -4,6 +4,9 @@ python_files = test_*.py
 python_classes = Test*
 python_functions = test_*
 
+# Python path for imports
+pythonpath = . tests
+
 # Test paths
 testpaths = tests
 
@@ -24,6 +27,7 @@ markers =
     integration: mark test as integration test
     smoke: mark test as smoke test
     slow: mark test as slow running
+    e2e: mark test as end-to-end test (requires real LangBot process)
 
 # Coverage options (when using pytest-cov)
 [coverage:run]