finegrained: address the integration review
One guard decorator on the DeepGEMM experts forwards instead of four statements
per body, and that file's comments cut to what is not already in the code.
`prefers_deepgemm_linear` moves to `deepgemm.py`, where its measured verdicts
belong, so the dispatcher just asks. `_FineGrainedModule.local(name)` is the one
accessor every forward reads operands through, so the DTensor unwrap appears
once rather than at seven call sites.
`_WeightFormat` is public (it is in `resolve_weight_format`'s signature), the
`TRANSFORMERS_FINEGRAINED_NO_SWIZZLE` debug hatch is gone (tests patch the
predicate), and `_set_optional_parameter` replaces six register-or-assign
blocks. `check_arch` is passed straight through: `kernels` is pinned >= 0.16,
where it landed, so the compatibility shim was dead.
The scalar-shard branch becomes `_owns_expert`, stated as the general fact it is
rather than as an NVFP4 anecdote. `FineGrainedConfig`'s docstring opens with a
format table. The frozen fp8 modules' `stacklevel=2` is dropped: at module scope
it named importlib rather than the module being deprecated.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
