fix(editor): improve result navigation and scrolling performance

apps/desktop/src/lib/__tests__/editor/deferredEditorTask.spec.ts

@@ -0,0 +1,45 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { createDeferredEditorTask } from "@/lib/editor/deferredEditorTask";
+
+afterEach(() => vi.useRealTimers());
+
+describe("deferred editor work", () => {
+  it("does no work during sustained scrolling and processes the final viewport once", () => {
+    vi.useFakeTimers();
+    let viewport = 0;
+    const publish = vi.fn(() => viewport);
+    const task = createDeferredEditorTask(publish, 150);
+    for (let frame = 0; frame < 100; frame++) {
+      viewport = frame * 20;
+      task.schedule();
+      vi.advanceTimersByTime(16);
+    }
+    expect(publish).not.toHaveBeenCalled();
+    vi.advanceTimersByTime(150);
+    expect(publish).toHaveBeenCalledOnce();
+    expect(publish).toHaveReturnedWith(1980);
+  });
+
+  it("flushes pending work before an owner switch without a later duplicate", () => {
+    vi.useFakeTimers();
+    let owner = "old-tab";
+    const publish = vi.fn(() => owner);
+    const task = createDeferredEditorTask(publish, 150);
+    task.schedule();
+    task.flush();
+    owner = "new-tab";
+    vi.runAllTimers();
+    expect(publish).toHaveBeenCalledOnce();
+    expect(publish).toHaveReturnedWith("old-tab");
+  });
+
+  it("cancels semantic refreshes when the editor plugin is destroyed", () => {
+    vi.useFakeTimers();
+    const refresh = vi.fn();
+    const task = createDeferredEditorTask(refresh, 100);
+    task.schedule();
+    task.cancel();
+    vi.runAllTimers();
+    expect(refresh).not.toHaveBeenCalled();
+  });
+});

apps/desktop/src/lib/editor/deferredEditorTask.ts

@@ -0,0 +1,23 @@
+/** Keep nonvisual work off continuous typing/scrolling, with an explicit lifecycle flush. */
+export function createDeferredEditorTask(run: () => void, delay: number) {
+  let timer: ReturnType<typeof setTimeout> | null = null;
+  function cancel() {
+    if (timer !== null) clearTimeout(timer);
+    timer = null;
+  }
+  return {
+    schedule() {
+      cancel();
+      timer = setTimeout(() => {
+        timer = null;
+        run();
+      }, delay);
+    },
+    cancel,
+    flush() {
+      if (timer === null) return;
+      cancel();
+      run();
+    },
+  };
+}