engine: mesh.size.* commands, honoured by every mesher (#435)

mesh.size.set adds a size control on faces, bodies, a box or a sphere;
mesh.size.growth sets the growth rate; mesh.size.clear and
mesh.size.list. The tet mesher bakes the controls into its graded field,
the hex meshers, cells and the octree take the graded RegionSize, and
the block projection and mesh plans divide their edges by it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/engine/src/cmd/cells.rs

@@ -28,7 +28,6 @@ use std::collections::{BTreeMap, BTreeSet};
 
 use fieldcraft_mesh::cdt::CdtOptions;
 use fieldcraft_mesh::hex::{Cell, CellsMesh, HexMesh, HexMethod, HexOptions, hex_mesh_swept_cells};
-use fieldcraft_mesh::size::UniformSize;
 use fieldcraft_mesh::surface::BoundarySurface;
 use fieldcraft_model::geometry::Entity;
 use fieldcraft_model::{ElementFace, GeometryRef, Model, Set, Tie};
@@ -173,7 +172,10 @@ fn cells(s: &mut Session, p: &Value) -> Result<Value> {
     if let Some(o) = hex_params.as_object_mut() {
         o.remove("order");
     }
+    // The cells are meshed at one size, so the size controls apply to all of them alike.
+    let sizing = super::sizes::sizing(s)?.joint(&names.iter().map(String::as_str).collect::<Vec<_>>());
     let (tet_options, quality) = quality_options(&tet_params, s.limits.max_tets as u64)?;
+    let tet_options = sizing.tet_options("", &tet_params, &tet_options);
     let cdt = CdtOptions { max_steiner: s.limits.max_steiner, max_tets: tet_options.max_tets };
 
     let seeds = super::seeds::edge_seeds(s)?;
@@ -204,7 +206,7 @@ fn cells(s: &mut Session, p: &Value) -> Result<Value> {
             .filter_map(|&i| shapes.get(i))
             .map(|shape| Ok(Input { seeds: seeds.clone(), ..super::hex::shape_input(shape, Some(tolerance))? }))
             .collect::<Result<_>>()?;
-        match swept_together(p, &inputs, m, quadratic, size, tolerance, &seeds)? {
+        match swept_together(p, &inputs, m, quadratic, size, tolerance, &seeds, &sizing)? {
             Ok(cm) => {
                 for &i in &members {
                     if let Some(slot) = joint.get_mut(i) {
@@ -229,7 +231,7 @@ fn cells(s: &mut Session, p: &Value) -> Result<Value> {
         let input = || Ok::<_, EngineError>(Input { seeds: seeds.clone(), ..super::hex::shape_input(shape, Some(tolerance))? });
         let hex = |m: HexMethod| -> Result<(Input<'static>, HexMesh)> {
             let b = input()?;
-            let mesh = hex_body(&hex_params, &b, m, quadratic, size)?;
+            let mesh = hex_body(&hex_params, &b, m, quadratic, size, &sizing)?;
             Ok((b, mesh))
         };
         let (cell, mut info) = match method {
@@ -363,8 +365,10 @@ fn swept_together(
     size: Option<f64>,
     tolerance: f64,
     seeds: &[fieldcraft_mesh::seeds::EdgeSeed],
+    sizing: &super::sizes::Sizing,
 ) -> Result<std::result::Result<CellsMesh, String>> {
     let h = size.ok_or_else(|| EngineError::Params("no element size".into()))?;
+    let field = sizing.field("", h)?;
     let mut surfaces = Vec::with_capacity(inputs.len());
     for b in inputs {
         let options = super::mesh::surface_options(p, &b.mesh)?;
@@ -382,7 +386,7 @@ fn swept_together(
         seeds: seeds.to_vec(),
         ..HexOptions::default()
     };
-    match hex_mesh_swept_cells(&cells, &UniformSize(h), &options) {
+    match hex_mesh_swept_cells(&cells, &field, &options) {
         Ok(cm) => Ok(Ok(cm)),
         Err(fieldcraft_mesh::Error::Model(fieldcraft_model::Error::Cancelled)) => Err(EngineError::Model(fieldcraft_model::Error::Cancelled)),
         Err(e @ fieldcraft_mesh::Error::Limit(_)) => Err(EngineError::Params(e.to_string())),