fix(tests): make the IP-Adapter slow test runnable again

[Anai-Guo]

Problem

tests/backend/ip_adapter/test_ip_adapter.py::test_ip_adapter_unet_patch cannot
run. It is @pytest.mark.slow, which the default
addopts = ... -m "not slow" excludes, so nothing surfaces it.

Three things are wrong:

1. It requests a model_installer fixture that does not exist anywhere in
   the tree.
2. It calls install_and_load_model(model_installer=...), but that parameter
   has been model_manager since the model-manager refactor
   (invokeai/backend/util/test_utils.py:24).
3. It requests torch_device, defined at
   invokeai/backend/util/test_utils.py:15 but not imported into any
   conftest, so pytest cannot resolve that one either.

tests/conftest.py line 5 still says

# We import the model_installer and torch_device fixtures here so that they can be used by all tests.

— but neither import is actually there any more.

Fix

• use mm2_model_manager (already star-imported into tests/conftest.py via
  tests.backend.model_manager.model_manager_fixtures) and pass it as
  model_manager=
• import torch_device in tests/conftest.py. That is what the comment already
  claims, and the same file documents this as the convention for fixtures that
  trip F401/F811 — importing it in the test module instead produces two F811s
  against build_dummy_sd15_unet_input(torch_device) and the test signature
• drop model_installer from that comment, and fix the docstring Args: entry
  in install_and_load_model, which still calls the parameter
  mm2_model_manager

Verification

The test downloads models, so I have not run it. What is checked statically —
signature parsed out of test_utils.py on main, fixtures grepped from the
actual files rather than code search:

install_and_load_model (model_manager, model_path_id_or_url, model_name, base_model, model_type, submodel_type=None)
  main     model_installer=... -> TypeError: install_and_load_model() got an unexpected keyword argument 'model_installer'
  this PR  model_manager=...   -> binds OK

  def model_installer(...)   defined in tests/conftest.py: False
  def mm2_model_manager(...) defined in tests/backend/model_manager/model_manager_fixtures.py: True
  def torch_device(...)      defined in invokeai/backend/util/test_utils.py: True

  conftest imports torch_device: False
  conftest defines model_installer: False
  conftest still names model_installer in a comment: True

ruff check and ruff format --check with the repo pyproject.toml report
exactly the same results on the patched files as on main — no new findings.

Happy to also just delete the test instead if it is considered dead; it looked
worth keeping since -m "slow" is a documented way to run it.

🤖 Generated with Claude Code