fix(model): restore saved solid booleans

Reload exact B-reps from solid history or ACIS before model operations and pin the closed-cut kernel fix.

src/scene/mod.rs

@@ -1645,11 +1645,7 @@ pub struct Scene {
     /// owning block emits a transformed instance so a block placed at an
     /// INSERT scale renders at the right size. (#123)
     pub block_meshes: HashMap<Handle, MeshLodSet>,
-    /// Live B-reps for solids created this session by the Model tab, keyed by
-    /// entity handle. Backs the Design-group boolean tools (a solid must be
-    /// here to be combined) and the exact-geometry save path, which writes
-    /// each one back out as ACIS rather than as facets. Not persisted —
-    /// rebuilt only by creating or combining primitives in-session.
+    /// Kernel B-reps used by solid operations and exact-geometry saves.
     pub solid_models: HashMap<Handle, cadkernel::brep::Body>,
     /// GPU render data for raster images (RasterImage entities), keyed by handle.
     pub images: HashMap<Handle, ImageModel>,