"""Shared, importable test helper utilities.

Submodules (``assertions``, ``env``, ``media``, ``runtime``, …) are imported
explicitly by callers. Avoid star-importing everything here: that ran before
refactor only inside the old monolithic ``conftest``; a greedy ``__init__``
changes import order and can affect in-process Omni (``OmniRunner`` / offline
e2e) vs subprocess-based ``OmniServer`` tests.
"""