fix(layers): disable redundant set current

Refs #459

src/app/update/command.rs

@@ -879,6 +879,9 @@ pub(super) fn on_tab_close(&mut self, idx: usize) -> Task<Message> {
                 if let Some(idx) = self.tabs[i].layers.selected {
                     if let Some(layer) = self.tabs[i].layers.layers.get(idx) {
                         let name = layer.name.clone();
+                        if name == self.tabs[i].layers.current_layer {
+                            return Task::none();
+                        }
                         // Mirror the change into the document header (CLAYER) too,
                         // not just the per-tab default. Otherwise the no-selection
                         // ribbon refresh (e.g. after Esc) re-reads the stale header

src/ui/window/layers.rs

@@ -328,6 +328,10 @@ impl LayerPanel {
             .selected
             .map(|i| self.layers.get(i).map(|l| l.name == "0").unwrap_or(false))
             .unwrap_or(false);
+        let can_set_current = self
+            .selected
+            .and_then(|i| self.layers.get(i))
+            .is_some_and(|layer| layer.name != self.current_layer);
 
         // ── Toolbar ───────────────────────────────────────────────────────
         let toolbar = container(
@@ -343,7 +347,7 @@ impl LayerPanel {
                     crate::ui::icons::CHECK,
                     t!("Set Current"),
                     Message::LayerSetCurrent,
-                    has_sel,
+                    can_set_current,
                 ),
                 iced::widget::Space::new().width(sizing.width),
                 // Search box: filters rows by name as the user types (#343).