rtx-cfd: OversetPisoSolver::momentum_residual — the background predictor's own staggered stencil (u_rhs/v_rhs, factored out of the predictor bit-identically) evaluated on every face of a NaN-masked field; solved faces read rounding, the active–fringe interface reads the composite's pressure level offset δ·h (cancels in the sum), prescribed fringe–fringe / fringe–hole faces read the stamping's momentum injection; hole ghosts (p, u, v) from a band widened three rows into the hole make every ring face evaluable; overset_cfd1 prints the buckets, the ring x-bands and δ at the settled state; pin: residual vanishes on the solved faces

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2

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

@@ -25,8 +25,10 @@
 //! nor the acceptor cells — is measured every step on both sides.
 
 pub mod overlap;
+pub mod residual;
 
 pub use overlap::{Acceptor, CellClass, DualDonor, FringeEntry, LatticeDonor, OverlapMap};
+pub use residual::{FaceResidual, MomentumResidual, ResidualBucket};
 
 use crate::error::{CfdError, CfdResult};
 use crate::mesh::PatchMesh;