fix(select): box/lasso-select blocks whose body is a solid

Box/lasso only tested top-level solid meshes, so a block whose visible body
is a solid (its mesh lives in the per-INSERT instanced cache, and it has no
wires to catch) was never picked up by a window/crossing/lasso. Add
block_mesh_box_hit / block_mesh_poly_hit that test each INSERT's instanced
block solid meshes and resolve a hit to the parent INSERT, and wire them
into the selection paths.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/update.rs

@@ -3742,6 +3742,9 @@ impl OpenCADStudio {
                                 handles.extend(
                                     self.tabs[i].scene.mesh_box_hit(a, p, crossing, vp_mat, bounds),
                                 );
+                                handles.extend(self.tabs[i].scene.block_mesh_box_hit(
+                                    a, p, crossing, vp_mat, bounds,
+                                ));
                                 // Box/lasso accumulates like individual picks
                                 // (issue #83): a plain box adds to the current
                                 // selection, Shift+box removes the boxed
@@ -3796,6 +3799,9 @@ impl OpenCADStudio {
                             handles.extend(
                                 self.tabs[i].scene.mesh_poly_hit(&poly_pts, crossing, vp_mat, bounds),
                             );
+                            handles.extend(self.tabs[i].scene.block_mesh_poly_hit(
+                                &poly_pts, crossing, vp_mat, bounds,
+                            ));
                             // Selection filter: keep only allowed types.
                             handles.retain(|&h| self.tabs[i].scene.passes_selection_filter(h));
                             // Accumulate like the box path (issue #83): plain
@@ -3935,6 +3941,9 @@ impl OpenCADStudio {
                             handles.extend(
                                 self.tabs[i].scene.mesh_box_hit(a, p, crossing, vp_mat, bounds),
                             );
+                            handles.extend(self.tabs[i].scene.block_mesh_box_hit(
+                                a, p, crossing, vp_mat, bounds,
+                            ));
                             // Selection filter: keep only allowed types.
                             handles.retain(|&h| self.tabs[i].scene.passes_selection_filter(h));
                             // Accumulate (issue #83): a plain box adds to the