Insert Reference panel: one Attach, labelled underlay tools, slide-out with Edit Reference and xref fading

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

src/modules/insert/xattach.rs

@@ -26,10 +26,10 @@ use crate::scene::Scene;
 
 pub fn tool() -> ToolDef {
     ToolDef {
-        id: "XATTACH",
-        label: "Attach XREF",
+        id: "ATTACH",
+        label: "Attach",
         icon: IconKind::Svg(include_bytes!("../../../assets/icons/blocks/insert.svg")),
-        event: ModuleEvent::Command("XATTACH".to_string()),
+        event: ModuleEvent::Command("ATTACH".to_string()),
     }
 }