embedded3 R6-2: the moving mask's classification on the device (RTX_E3_MASK_DEVICE=1, needs RTX_E3_GEOM_DEVICE=1)

- e3_mask.cu: the changed set (touched by either build, dilated), the faces of
  the changed cells, per changed cell the fluid flag / space-time activity /
  GCL entry and the merging master, per face the kind, the step aperture and
  open flag and the open-part centroid shift (compute_face_shifts' cv
  geometry), the GCL table's wall cells / areas / table with the correction,
  the merged cells' CSR (slave ranks from the master's distinct face
  neighbours), the imposition band's faces; block scans for ascending stream
  compaction and the CSR's exclusive scan. fp64, FMA contraction off.
- step/device/mask.rs DeviceMask: snapshots the previous apertures / volumes /
  evaluated cells before the R6-1 geometry kernels, runs the classification
  into DeviceCut's persistent tables (a, open, open_pred, active,
  active_pred, owner, shift, wall_flux, fold_ptr/fold_idx) and returns the
  compact values (MaskUpdate); the GCL sums in ascending order on the host.
  DeviceCut::update_after_device_mask: only the band's surface velocities
  remain (band list compacted on the device).
- maskupdate.rs: Mask::from_update — the host mirror from the old mask's step
  arrays and merging map (moved) and the mask retired a step earlier
  (instantaneous arrays, pooled), the compact values scattered; incremental
  fluid count / anchor / side check; the fresh-cell refill over the changed set.
- RTX_E3_BAND_CHECK=1 with the knob: the host rebuild on copies (from_cut,
  face shifts, step apertures, merging, GCL, refill) against the mirror, bit
  for bit, and every device table against a full build.
- Knob off: the host path unchanged (Mask::from_parts, Solver::configure_mask
  and retire_mask are the same statements); profile laps under
  RTX_E3_MOVING_PROFILE only.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

crates/specialized/rtx-cfd/src/solvers/incompressible/embedded3/mod.rs

@@ -16,6 +16,7 @@ pub mod field;
 pub mod grid;
 pub mod impose;
 pub mod loads;
+pub mod maskupdate;
 pub mod poisson;
 pub mod reconstruct;
 pub mod step;