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/doc/src/feature_walk_tests/fixtures.rs

@@ -158,6 +158,7 @@ pub(super) fn fixtures() -> Vec<(&'static str, Value)> {
                 "orientation": "parallel", "twist": "surface_sweep.twist", "scale": "surface_sweep.scale"}),
         ),
         ("surface_loft", json!({"type": "surface_loft", "sections": []})),
+        ("surface_blend", json!({"type": "surface_blend", "from": {"body": "B", "edges": [o]}, "to": {"body": "C", "edges": [o]}, "align": [o, o]})),
         ("surface_offset", json!({"type": "surface_offset", "faces": [o], "distance": "soff.distance", "tolerance": "soff.tolerance"})),
         ("unstitch", json!({"type": "unstitch", "body": "B"})),
         ("reverse_normal", json!({"type": "reverse_normal", "body": "B"})),

crates/doc/src/feature_walk_tests/golden_exprs.txt

@@ -328,6 +328,7 @@ surface_sweep_options
     Scale = surface_sweep.scale (Unitless)
   expressions: surface_sweep.twist, surface_sweep.scale
 surface_loft
+surface_blend
 surface_offset
   inputs:
     Distance = soff.distance (Length)

crates/doc/src/feature_walk_tests/golden_geometry.txt

@@ -147,6 +147,8 @@ surface_revolve
 surface_sweep
 surface_sweep_options
 surface_loft
+surface_blend
+  moves: align[0][0], align[0][1], align[0][2], align[1][0], align[1][1], align[1][2], from.edges[0][0], from.edges[0][1], from.edges[0][2], to.edges[0][0], to.edges[0][1], to.edges[0][2]
 surface_offset
   moves: faces[0][0], faces[0][1], faces[0][2]
   face points: [0, 0, 0]

crates/doc/src/feature_walk_tests/golden_refs.txt

@@ -169,6 +169,8 @@ surface_sweep_options
 surface_loft
   sketches: [4, 5]
   remap_refs: sections[0].sketch, sections[1].sketch
+surface_blend
+  remap_bodies: from.body
 surface_offset
   remap_bodies: body
 unstitch