e3_geom_ub / e3_geom_impose / e3_geom_seam: the flag body's surface velocity (DeviceSdf::vel, the centreline's velocity per point) at the foot from the trilinear interpolant of the device corner phi, and at the face centre for the band's solid faces of the uploaded field (a cut mask has no ghosts); the host mirror of ub by a packed download. RTX_E3_BAND_CHECK=1 compares the device ub with Mask::surface_velocity_at and the imposed u, v, w with impose_from, bit for bit; check_against now compares ub on every band face (zeros included). Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>