ENH: Upstream ResampleSeries resampling engine from fMRIPrep

Summary

fMRIPrep contains the core one-shot resampling engine for EPI time series in fmriprep/interfaces/resampling.py. This is the most architecturally significant piece of fMRIPrep code that should be shared across NiPreps.

ResampleSeries interface + resample_image / resample_vol / resample_series functions

The core one-shot resampling engine that combines:

• Per-volume HMC transform application (VOX2VOX)
• Fieldmap-based coordinate displacement with PE direction
• Jacobian intensity correction
• Async concurrent per-volume resampling

The modality-agnostic core (resample_vol, async infrastructure) can serve as the shared resampling engine for fMRIPrep, dMRIPrep, and NiBabies.

Supporting utility: asynctools.worker (fmriprep/utils/asynctools.py)

Async semaphore-gated worker function for concurrent resampling.

Code to upstream

• ResampleSeries Nipype interface
• resample_image, resample_vol, resample_series functions
• asynctools.worker utility

Rationale

• dMRIPrep needs essentially identical one-shot resampling (with DWI-specific adaptations)
• The core resample_vol function is modality-agnostic
• NiTransforms is the natural home for the reference resampling implementation
• This would become the shared resampling engine for the entire NiPreps ecosystem

Priority

HIGH — cornerstone of the transform stage, critical for dMRIPrep.

Start by reading fmriprep/interfaces/resampling.py and fmriprep/utils/asynctools.py, focusing on ResampleSeries, resample_image, resample_vol, resample_series, and worker. Determine how these components should be shared in NiTransforms; done means the listed interface, functions, and utility are upstreamed for reuse by fMRIPrep, dMRIPrep, and NiBabies.