DCPInvariant v0.3.0

DCPInvariant v0.3.0 adds one fixed asynchronous-checkpoint snapshot witness
to the existing bounded PyTorch Distributed Checkpoint evidence suite.

The new async_snapshot_resnet18_2r scenario uses two local CPU/Gloo ranks,
torchvision.models.resnet18(weights=None), synthetic input, and a controlled
public StorageWriter gate. It verifies that the checkpoint loaded before
promotion matches the staged pre-mutation state, differs from the post-mutation
state, and remains receipt-bound after promotion.

The schema-v3 evidence archive contains 12 fixed scenarios. Its offline
verifier reports all 12 passed and binds the source revision, PyTorch 2.11,
torchvision 0.26, Pillow 12.3, and NumPy 2.4.6 runtime contract. The attached
SHA256SUMS binds the wheel, source distribution, and evidence archive.

This release is fixture-, version-, topology-, and single-host CPU/Gloo-bound.
It does not establish arbitrary-model snapshot semantics, performance or
speedup, dynamic membership change, more than two processes, multi-node,
GPU/NCCL, FSDP, production reliability, external adoption, independent
review, or recruiting outcomes.

Original DCPInvariant code is released under Apache-2.0. Third-party software
is not redistributed except for license and provenance notices included in
the source distribution.