fix: Layer rename targets active layer + rename field width

- active-layer property now updated on switch_layer callback
  (rename was always targeting layer 0)
- Rename input constrained to 85px max-width (no overflow)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main.rs

@@ -453,6 +453,7 @@ fn main() {
                         layers.set_row_data(i, item);
                     }
                 }
+                w.global::<KeymapBridge>().set_active_layer(layer_index);
                 w.global::<AppState>().set_status_text(SharedString::from(format!("Loading layer {}...", idx)));
             }
             let serial = serial.clone();

ui/tabs/tab_keymap.slint

@@ -58,6 +58,7 @@ export component TabKeymap inherits VerticalLayout {
             if root.renaming : VerticalLayout {
                 spacing: 4px;
                 rename-input := DarkLineEdit {
+                    max-width: 85px;
                     placeholder-text: "New name";
                     accepted(text) => {
                         KeymapBridge.rename-layer(KeymapBridge.active-layer, text);