fix(dimension): render baked *D fills inside block dimensions

A dimension bakes its geometry into a per-instance *D block, offset into
the owning block by the dimension insertion_point. When that dimension
sits inside a block (INSERT → block → Dimension → *D), only its top-level
form drew; nested it rendered nothing, and once the lines/text/arrow
outlines were routed through the block cache the arrowhead FILLS were
still missing:

- 2D SOLID arrowheads: block_cache's Dimension arm now expands the *D
  block, translating each sub by insertion_point (WCS → block-local) and
  routing Insert subs through build_nested_ref, others through
  tessellate_sub_local (which emits the solid fill_tris).
- Insert(hatch) arrowheads (custom arrow blocks = LwPolyline + Hatch):
  the hatch renders via the separate GPU explosion path, which only
  descends INSERT→INSERT→Hatch trees and so never reached a hatch behind
  a Dimension. block_has_hatch now recurses through a Dimension into its
  *D block, and the fill explosion's new explode_including_dims lifts
  each dimension child's *D content into the owning block's frame
  (translate insertion_point, then apply the insert transform) so its
  arrow inserts / hatches ride the normal walk.

Table *T baked blocks get the mirror treatment in block_cache.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scene/mod.rs

@@ -4092,6 +4092,14 @@ impl Scene {
                 br.entity_handles.iter().any(|&h| match self.document.get_entity(h) {
                     Some(EntityType::Hatch(_)) => true,
                     Some(EntityType::Insert(ins)) => self.block_has_hatch(&ins.block_name, memo),
+                    // A dimension bakes its geometry into a per-instance `*D`
+                    // block; a custom filled arrowhead lives there as a nested
+                    // Insert(hatch). Recurse so the fill explosion knows to
+                    // descend the dimension (see `explode_including_dims`).
+                    Some(EntityType::Dimension(dim)) => {
+                        !dim.base().block_name.trim().is_empty()
+                            && self.block_has_hatch(&dim.base().block_name, memo)
+                    }
                     _ => false,
                 })
             })