Engine: mesh.cells meshes a partitioned part cell by cell

Each cell (a body of the open design) gets its own method: structured hex where
one fits (auto falls back to tet and says why), or tet. All go into one mesh.
Cells on either side of a partition are joined: where their element faces
match node for node the nodes are merged; otherwise (hex next to tet, or
different divisions) the two partition faces get a set each and a dual mortar
tie, the reported hex-tet transition. A 40 mm bar cut in half, one half hex,
the other tet, stretches F L / (E A) to 1e-6.

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

crates/engine/src/catalogue.rs

@@ -286,12 +286,13 @@ pub static CATALOGUE: &[Capability] = &[
         "Hex mesh swept along extrusions (several levels), around revolutions, or from a source face to a target",
         &["mesh.hex.generate"],
     ),
-    ready(
+    ready_more(
         "mesh.hex.blocks",
         "Block Hex",
         Mesh,
         "Structured Hex",
         "One conforming hex mesh of a part split into six-sided blocks: shared faces meshed once",
+        &["mesh.cells"],
     ),
     soon("mesh.hex.decompose", "Decompose", Mesh, "Structured Hex", "M5", "Find sweepable and mappable regions and propose the splits"),
     soon("mesh.transition", "Transition", Mesh, "Structured Hex", "M5", "Conforming tet–hex interfaces with pyramids"),