UI: another dialog never replaces the open macro step editor

The step editor lives in the app's one dialog slot, so Format Cells, the Macros
dialog or New Macro opened while it was up took its place. The draft was lost
(New Macro started a fresh one), and a closed-over editor left its grid overlays and
its debug run behind. While the editor is open, requests for other dialogs are now
ignored; the editor closes itself as before.

crates/ui-egui/src/lib.rs

@@ -826,6 +826,9 @@ impl SheetApp {
                 let page = params.get("page").and_then(Json::as_str).and_then(backstage::Page::parse).unwrap_or(backstage::Page::Home);
                 self.open_backstage(page);
             }
+            // The macro step editor stays until it closes itself (its draft, overlays and debug
+            // run go with it), so another dialog can't replace it.
+            _ if self.dialog.as_ref().is_some_and(|d| d.name == "macroEditor") => {}
             other => self.dialog = dialogs::Dialog::open(self, other, params),
         }
     }

crates/ui-egui/tests/it/macro_editor.rs

@@ -269,3 +269,19 @@ fn a_rename_that_lands_before_a_failed_save_is_remembered() {
     assert_eq!(wb.macros.len(), 1);
     assert_eq!((wb.macros[0].name.as_str(), wb.macros[0].steps.len()), ("Renamed", 3));
 }
+
+#[test]
+fn another_dialog_never_replaces_the_open_editor() {
+    let mut h = harness();
+    three(&mut h);
+    h.state_mut().macros.editor.as_mut().unwrap().draft.name = "Unsaved".into();
+    h.run_steps(2);
+    for name in ["formatCells", "macros", "macroEditor"] {
+        h.state_mut().open_dialog(name, json!({}));
+        h.run_steps(2);
+        assert_eq!(h.state().dialog.as_ref().map(|d| d.name.as_str()), Some("macroEditor"), "{name}");
+        assert_eq!(h.state().macros.editor.as_ref().map(|e| e.draft.name.as_str()), Some("Unsaved"), "{name}");
+    }
+    click(&mut h, "New Macro");
+    assert_eq!(h.state().macros.editor.as_ref().map(|e| e.draft.name.as_str()), Some("Unsaved"));
+}