Some test files (e.g. test_llm_core_sanitize_tool_calls) stub
sqlalchemy and core.database at module level with
`if mod not in sys.modules`. During pytest collection these stubs
fire before the real modules are imported, contaminating every
subsequent test that needs real ORM objects (IntegrityError, missing
columns, etc.).
Pre-import the real modules in conftest.py so the module-level
guards find them already loaded and skip the stubs. Fixes ~10+
cascading test failures that only appear in the full suite.
Fixes#2395
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
