REFEDIT: reference prompts, -REFEDIT, REFSET, nested references, xref write-back

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/update/file.rs

@@ -866,6 +866,7 @@ impl OpenCADStudio {
             block_mru_list: self.block_mru_list,
             block_redefine_mode: self.block_redefine_mode,
             block_navigate: self.block_navigate.clone(),
+            xfadectl: crate::scene::cache::block_cache::refedit_fade_ctl() as u8,
             count_color: self.count_palette.color,
             count_error_color: self.count_palette.error_color,
             count_service: self.count_palette.service,
@@ -1019,6 +1020,7 @@ impl OpenCADStudio {
         self.block_mru_list = s.block_mru_list.min(100);
         self.block_redefine_mode = s.block_redefine_mode.min(2);
         self.block_navigate = s.block_navigate.clone();
+        crate::scene::cache::block_cache::set_refedit_fade_ctl(i32::from(s.xfadectl.min(90)));
         self.count_palette.color = s.count_color;
         self.count_palette.error_color = s.count_error_color;
         self.count_palette.service = s.count_service;