Add slow modular-pipeline integration tests with declared offload behavior
Every recorded offload event now carries the device's cumulative peak-memory
reading (never reset by the offloader, so deltas between consecutive events
attribute activation peaks to the interval between moves).
New ModularPipelineIntegrationTesterMixin runs a modular pipeline against its
real checkpoint: subclasses declare the expected offloading behavior per
simulated card (offload counts, OOM-retry counts, final device per model) and
test_auto_cpu_offload_on_cards verifies the run matches the spec and leaves
the output untouched. The docstring carries the discovery recipe for
transcribing a new pipeline's behavior from the offload record.
TestZImageModularIntegration exercises Z-Image-Turbo on 32/24/16/10GB cards
(no offloading / text encoder yields / transformer also yields / run-alone
escape hatch) plus text-to-image and image-to-image slice checks.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>