feat(xref): wider panel default, Attach DWG/Image/PDF menu, status icons

External References dock default 360 to 460 for the column-rich table. Attach split button reads Attach DWG with Attach Image and Attach PDF options, all menu rows full width. List view shows one distinct glyph and theme color per reference status.

src/ui/dock.rs

@@ -59,7 +59,7 @@ impl PanelId {
         match self {
             PanelId::Properties => 250.0,
             PanelId::BlockPalette => 260.0,
-            PanelId::ExternalReferences => 360.0,
+            PanelId::ExternalReferences => 460.0,
         }
     }
 
@@ -239,9 +239,9 @@ mod tests {
     fn external_references_allows_double_max_width() {
         let mut state = DockState::default();
         state.ensure_settings();
-        // Slightly wider default than the 300-era panels, double the maximum.
+        // Wider default for the column-rich references table, double the maximum.
         // (The 45%-of-window rule still dominates on narrow windows.)
-        assert_eq!(state.width(PanelId::ExternalReferences, 3000.0), 360.0);
+        assert_eq!(state.width(PanelId::ExternalReferences, 3000.0), 460.0);
         state.set_width(PanelId::ExternalReferences, 5000.0);
         assert_eq!(state.width(PanelId::ExternalReferences, 3000.0), DOCK_MAX_W * 2.0);
         // Other panels keep the shared maximum.