PDF underlays: attach dialog with pages, underlay tab, layers, import settings and file import, unload on the definition

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

src/app/commands/display.rs

@@ -1861,7 +1861,8 @@ impl OpenCADStudio {
                 }
             }
 
-            "POINTCLOUDATTACH" | "RECAP" | "SYNCPVIEWPORTS" | "UNDERLAYLAYERS" => {
+            "UNDERLAYLAYERS" | "ULAYERS" => self.open_underlay_layers_dialog(i),
+            "POINTCLOUDATTACH" | "RECAP" | "SYNCPVIEWPORTS" => {
                 self.command_line
                     .push_info(crate::tf!("{cmd}: not yet implemented.").as_ref());
             }