fix(editor): auto-save when the app is deactivated while focus is in a frame (#1636)

With focus in a plugin's web view, the window's blur fires when the frame takes focus, before any edit, and not again when the user switches applications, so edits made in the frame weren't auto-saved. The editor now also saves on the application-deactivated event.

src/editor/core/controller.ts

@@ -353,6 +353,8 @@ export class EditorController implements SlotHost {
         void this.saveCustomDocuments(true).catch((e) => this.documentError(e));
       }
     };
+    if (this.manager.backend.onApplicationDeactivated)
+      this.disposers.push(this.manager.backend.onApplicationDeactivated(onWindowBlur));
     const onPageHide = () => this.saveSession();
     if (typeof window !== "undefined") {
       if (this.manager.backend.syncFromDisk)