mesh: the tet objective sees needles; no tet below scaled Jacobian 0.3 on the skill's tet parts

The improvement objective was the smallest dihedral sine, which misses
needles: every dihedral angle fine while a corner is nearly flat, so
the corpus meshes had scaled Jacobians down to 0.01-0.07. The objective
is now the smaller of the dihedral sine and the scaled Jacobian at the
worst corner (the measure analysts check, Knupp 2001), weighted so a
Jacobian of 0.3 (the skill's limit) counts as a 30 degree dihedral
angle (the schedule's target): the Jacobian decides only near that
limit. The existing edge removal, multi-face removal, smoothing and
insertion then remove the needles.

Skill tet10 min SJ: sphere-on-plate 0.092 -> 0.335, filleted-bracket
0.021 -> 0.318 (both pass, nothing marked). Default-size tet10:
thin-ribs 0.240, shallow-groove 0.321, rounded-box 0.311.

The strong-relaxation test relaxes below 0.45: nothing is left below
0.3. Literature note in docs/meshing/literature.md.

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

crates/mesh/src/tet/tests.rs

@@ -433,7 +433,17 @@ mod determinism {
         let (p, t, f) = washer();
         let m = mesh(&p, &t, &f);
         assert!(m.elements.len() > 100, "{:?}", m.report);
-        assert_eq!(fingerprint(&m), 6_285_915_972_108_509_003, "{} tets, {} nodes", m.elements.len(), m.points.len());
+        // No needles either: the scaled Jacobian analysts check is above the skill's limit.
+        let sj = m
+            .elements
+            .iter()
+            .map(|e| {
+                let xyz: Vec<[f64; 3]> = e.iter().map(|&v| m.points[v as usize]).collect();
+                crate::quality::element_quality(m.kind, &xyz).unwrap().get(crate::quality::Metric::ScaledJacobian).unwrap()
+            })
+            .fold(f64::INFINITY, f64::min);
+        assert!(sj >= 0.3, "min scaled Jacobian {sj}");
+        assert_eq!(fingerprint(&m), 11_252_377_805_886_396_373, "{} tets, {} nodes", m.elements.len(), m.points.len());
     }
 
     /// Listing the triangles, their corners and the vertices in another order, and numbering