feat(record): capture Trace v3 states after pages settle

Wait for DOM quiet after actions, match targets to VOM refs, and reduce
drafts into deduped state-linked Trace v3 while keeping the v2 reducer.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/extension/src/lib/__tests__/page-settled.test.ts

@@ -0,0 +1,43 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import type { CdpRunner } from "@/tools/shared";
+import { waitForPageSettled } from "../page-settled";
+
+function quietCdp(): { cdp: CdpRunner; send: ReturnType<typeof vi.fn> } {
+  const send = vi.fn(async () => ({
+    result: { value: { idleMs: 1_000, readyState: "complete" } },
+  }));
+  return {
+    cdp: { send: send as unknown as CdpRunner["send"] },
+    send,
+  };
+}
+
+describe("waitForPageSettled", () => {
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("waits through the minimum observation floor before accepting a quiet page", async () => {
+    vi.useFakeTimers();
+    const { cdp, send } = quietCdp();
+
+    const settled = waitForPageSettled(cdp, 7);
+    await vi.advanceTimersByTimeAsync(180);
+
+    await expect(settled).resolves.toBe("quiet");
+    expect(send).toHaveBeenCalledTimes(3);
+  });
+
+  it("cancels before probing a superseded observation", async () => {
+    vi.useFakeTimers();
+    let cancelled = false;
+    const { cdp, send } = quietCdp();
+
+    const settled = waitForPageSettled(cdp, 7, { cancelled: () => cancelled });
+    cancelled = true;
+    await vi.advanceTimersByTimeAsync(60);
+
+    await expect(settled).resolves.toBe("cancelled");
+    expect(send).not.toHaveBeenCalled();
+  });
+});