New initial-condition generator resampled_velocity starts a periodic-box case from an existing velocity field: a published DNS, an experiment, another code's snapshot, or a field at another resolution. It reads raw binary, .npy, .npz or HDF5 (with h5py installed) through a declared layout, moves the field to the case's grid in Fourier space with an optional filter, and makes it divergence-free for PICurv. By default it stages face fluxes, which keep more of the field's energy than cell-centre velocities: 87% against 78% for the AGARD HOM02 DNS field on a 64-cubed grid. Page 33 explains when to use it rather than mode: file.
mode: file now refuses, before the solver starts, a field sized for a different grid, and names resampled_velocity as the way to bring such a field in.
picurv run and picurv sweep report a failure to build a case's inputs as a [FATAL] message instead of a Python traceback.