fix(viewport): apply per-viewport layer freeze to fills, images and meshes

A content viewport that froze layers still drew those layers' hatches,
2-D solids, images, OLE frames and 3-D solids — only its wires honoured
`Viewport.frozen_layers`. A viewport meant to be empty (all content
layers frozen) leaked the whole model instead.

viewport_data_for fed content viewports the full model hatch/wipeout/
image/mesh sets with no per-viewport frozen filter. Thread the viewport's
frozen-layer set through the builders (synced_hatch_models,
exploded_insert_hatch_models, wipeout_models, image_models, mesh_models,
instanced_block_meshes) via Scene::layer_frozen_in — the same
layer-name→handle→membership test the wire path uses — and expose
*_for_viewport accessors that cache the filtered set per order-independent
frozen-set signature (viewports sharing a frozen set share the build; an
empty set returns the shared unfiltered arc, so model tiles and
non-freezing viewports are byte-identical).

Each viewport renders in its own pipeline slot with the hatch upload
gated on geometry_epoch, so a per-viewport filtered set uploads once per
epoch rather than every frame.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/paper.rs

@@ -238,7 +238,7 @@ impl Scene {
         } else {
             self.bg_color
         };
-        let exploded = self.exploded_insert_hatch_models(layout_block, hatch_bg, false);
+        let exploded = self.exploded_insert_hatch_models(layout_block, hatch_bg, false, None);
         models.extend(exploded);
         Arc::new(models)
     }