fix(view): keep named views of earlier versions at their place, in f64

A VIEW record's centre is an offset from its target in view coordinates.
Views saved by earlier versions stored the target itself as the centre;
treating that as an offset put them (and VIEW plots) at about twice the
coordinates. One shared `named_view_center` now resolves the centre in
f64 (DVec3/DQuat), taking a centre equal to a non-zero target as the old
convention; VIEW RESTORE, the view plot window and Place on Sheet use it.

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

src/scene/mod.rs

@@ -37,6 +37,7 @@ pub use page_setup::{apply_default_page_setup, document_page_setups, rotated_mar
 mod dwg_native_constraints;
 mod entity;
 pub use entity::CreateBlockOptions;
+pub use camera_ops::named_view_center;
 #[cfg(test)]
 mod hatch_boundary;
 mod group_layer;