Show a bounded native-cache preview before authoritative reconstruction (#463)

Refs #303. file.save / file.save_as can store a warm native geometry cache (cache: true, off by default) keyed to the document hash, app version and adapter revision. Opening shows a bounded preview from it until the rebuilt session replaces it. Any cache failure counts as a miss.

vendor/README.md

@@ -46,6 +46,12 @@ Changes:
 ## truck-meshalgo 0.4.0 (Apache-2.0, © RICOS Co. Ltd., https://github.com/ricosjp/truck)
 
 Changes:
+- `tessellation/mod.rs`, `triangulation.rs`: a separate provisional `preview_face`
+  path accepts at most 4,096 already sampled boundary points and a fixed grid of
+  at most 16 subdivisions per direction, including periodic seam connections.
+  It does not run adaptive subdivision or grid balancing. The kernel caller bounds
+  projection complexity and total allocation before using it; ordinary modelling
+  tessellation keeps its existing accuracy policy.
 - `tessellation/triangulation.rs`: the inside test of a face's boundary skips loops whose
   parameter box is clear of the point (it tested every segment of every loop, so a face with
   hundreds of holes meshed in quadratic time).