embedded3 R6-1: the body's φ and the cut geometry on the device (RTX_E3_GEOM_DEVICE=1)

- e3_geom.cu: corner φ on the narrow band (the flag test's circle + capsule
  around the step's centreline polyline + span cuts + fillet union), face
  apertures / face-centre φ by the Kuhn triangles, cell volumes by the six
  Kuhn tets and wall vectors by closure — CutGeometry::build_from in fp64,
  host operation order, FMA contraction off.
- Body::with_device_sdf / DeviceSdf: the device form of φ (the host passes the
  polyline per step); the flag wake test attaches it (same arithmetic as its
  closure; the polylines factored out unchanged).
- step/device/geom.rs DeviceGeom: persistent φ / bound / volume / wall buffers;
  the face tables written straight into DeviceCut's predictor apertures and
  distances (update skips their scatters); the host mirror = the band's entries
  gathered compactly onto recycled arrays of retired device generations
  (GeomPool; band-list history) — Mask::from_cut classifies it.
- RTX_E3_BAND_CHECK=1 with the knob: mirror AND device tables against the host
  build_from bit for bit on every refresh.
- Knob off: byte-identical (slab ny 62 one period CSV = main's); host suite 21/21.

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

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

@@ -21,7 +21,7 @@ pub mod reconstruct;
 pub mod step;
 pub mod wall;
 
-pub use body::{Body, SurfaceSample};
+pub use body::{Body, DeviceSdf, SurfaceSample};
 pub use cut::CutGeometry;
 pub use export_vtk::write_vtk;
 pub use field::Field;