fix(wblock): exported drawings carry their block definitions and styles

WBLOCK copied only the entities and their layers, so INSERTs pointed at
missing blocks and the file opened almost empty or needed recovery. It
now goes through the cross-drawing paste kernels, which bring layers,
linetypes, styles, block definitions and baked dimension blocks along.

Fixes #1111

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/command_driver/mod.rs

@@ -94,7 +94,9 @@ mod text_edit;
 mod constraint;
 mod dim_edit;
 
-pub(crate) use clipboard::{copy_to_clipboard_kernel, remap_ext_subtree_reference};
+pub(crate) use clipboard::{
+    copy_to_clipboard_kernel, paste_entities_kernel, remap_ext_subtree_reference,
+};
 
 impl OpenCADStudio {
     /// Applies one command result, then — when that result ended the active