plot styles: the CTB/STB model and codec come from the codec crate

Cargo: codec d36331d, kernel 60f086b, graph 74aac56.

The table model and its file codec now live in `codec::plot_style`
(opencadcodec#53) and are re-exported here. What stays is where tables
come from: the plot styles folder, the session registry, the shipped
tables, and saving to disk, as the `PlotStyleTableExt` trait.

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

src/io/mod.rs

@@ -51,6 +51,8 @@ pub mod windows_media;
 pub mod xref;
 pub mod xref_model;
 
+#[cfg(not(target_arch = "wasm32"))]
+use crate::io::plot_style::PlotStyleTableExt as _;
 use crate::scene::DerivedCaches;
 use codec::entities::EntityType;
 // The path-based readers are native-only; web parsing runs through the