hex: conforming multi-block meshes of partitioned parts

hex_mesh_cells meshes cells that meet face to face (SolidCraft split
bodies) as one conforming all-hex mesh: each cell a mapped block after
smoothly meeting faces are joined (virtual topology: the halves of a hole,
a plane running into a fillet), vertices, edges and faces shared by
identity, interval assignment over all cells, each shared face meshed
once, radial edges graded off curved faces. finish spans several cells:
tags per cell, hex20 mid-edge nodes shared across cells, a closed
2-manifold boundary and no free internal face.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

crates/mesh/src/quad/tfi.rs

@@ -21,7 +21,7 @@ fn dist<const D: usize>(a: &[f64; D], b: &[f64; D]) -> f64 {
 }
 
 /// Normalized cumulative arc length of a side, from 0 to 1.
-fn params<const D: usize>(side: &[[f64; D]], name: &str) -> Result<Vec<f64>> {
+pub(crate) fn params<const D: usize>(side: &[[f64; D]], name: &str) -> Result<Vec<f64>> {
     let mut acc = Vec::with_capacity(side.len());
     let mut s = 0.0;
     acc.push(0.0);