Constrained Delaunay tetrahedralization (boundary recovery) and mesh.tet.generate (M2) (#29)

* predicates: LNC points, generic insphere and its perturbed form (Diazzi et al. 2023 §4.3)

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

* mesh: constrained Delaunay tetrahedralization (segment recovery with LNC Steiner points, gift-wrapping facet recovery, labelling)

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

* cdt: rounding repair, mesh.tet.generate, corpus CDT column; review cleanups (shared perturbation rule, one facet scan, cached coordinates, worklist segment recovery)

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

* mesh.tet.generate is ready in the catalogue; corpus table with the CDT column

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

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Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/mesh/src/predicates/interval.rs

@@ -27,6 +27,16 @@ impl Interval {
         if lo.is_nan() || hi.is_nan() { Self::NAN } else { Self { lo: lo.next_down(), hi: hi.next_up() } }
     }
 
+    /// The lower bound.
+    pub(crate) fn lo(&self) -> f64 {
+        self.lo
+    }
+
+    /// The upper bound.
+    pub(crate) fn hi(&self) -> f64 {
+        self.hi
+    }
+
     /// The midpoint, an approximation of the value.
     pub(crate) fn mid(&self) -> f64 {
         0.5 * self.lo + 0.5 * self.hi