Adds is_remote_vae_available(), get_endpoint_names(), _companion_decode()
plus INSTALL_INSTRUCTIONS constant. Lazy try-import of the companion module
returns a clear error if not installed. Old code paths still active; the
remote_decode_hf -> _companion_decode swap lands in the next task.
Also updates tests/conftest.py to load the real remote_vae module (via
importlib.util) so facade tests exercise actual code rather than a stub.
Adds network_utils real-load and diffusers/diffusers.image_processor stubs
to satisfy the remote_vae.py import chain in the test environment.
Jason Hoku
e5f690eae5