Class-A surfacing 1/3: the continuity core, a G3 free-form blend and patch crown (#1249)

The continuity core (kernel bridge: Hermite control rows reproducing a support surface's position, tangent, curvature and change of curvature, G0 to G3), surface.blend between two edge chains (#764), and a crown for fitted patches. Existing patches and fillets are unchanged by default (crown 0 is the plain patch bit for bit). SurfaceBlend and Patch.crown are noted under format 22.

crates/kernel/src/lib.rs

@@ -22,6 +22,7 @@ mod boolean_diagnostics;
 mod boolean_guard;
 mod boolean_record;
 mod bore_guard;
+mod bridge;
 mod build;
 mod clearance;
 mod coplanar;
@@ -117,12 +118,14 @@ pub use blend_corner::fillet_radii;
 pub use blend_variable::{RadiusSpline, Taper, fillet_chord, fillet_tapered, fillet_variable, fillet_variable_points, fillet_variable_spline, taper};
 pub use body::{Body, CapSignature, DISPLAY_ANGLE, EdgeInfo, FaceInfo, FacePaint, FaceSource, Paint};
 pub use boolean_diagnostics::{BooleanDiagnostics, BooleanFallback, BooleanStrategy, capture_boolean_diagnostics};
+pub use bridge::{Continuity, Frame, blend_between, bridge, chain, chain_closes, frames, sample_grid};
 pub use build::{
     PathSeg, box_solid, canonical_revolve_axis, cylinder, extrude, extrude_tapered, extrude_tapered_between, loft, revolve, sphere, sweep,
     sweep_with, torus,
 };
 pub use delete_face::delete_faces;
 pub use emboss::{cylinder_emboss_anchor, emboss_cylinder, emboss_cylinder_at, has_cylinder_emboss_wall, infer_cylinder_emboss};
+pub use fill::patch_edges_crowned;
 pub use helix::{loft_to_point, sweep_helix, sweep_helix_mesh};
 pub use iges_in::{MAX_IGES_BYTES, iges_import, iges_to_step};
 pub use iges_out::iges_export_bodies;