fix(paste): pasted entities land in the current space

The paste kernel added every entity to model space. It now takes the
space a new entity goes to: the block being edited, a layout's paper
space when no viewport is active, or model space.

Fixes #1652

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

src/app/mod.rs

@@ -9,7 +9,7 @@ pub(crate) mod config;
 pub use automation::{export_headless, serve};
 mod annotation_data;
 mod command_driver;
-pub(crate) use command_driver::{copy_to_clipboard_kernel, paste_entities_kernel};
+pub(crate) use command_driver::{copy_to_clipboard_kernel, paste_entities_kernel, PasteSpace};
 pub(crate) mod commands;
 pub(crate) mod dim_viewport;
 #[cfg(test)]