refactor: simplify workbench layout and browser tests

tests/browser/agent-acrylic.e2e.ts

@@ -1,4 +1,19 @@
 import { expect, test, type Locator } from "@playwright/test";
+import { mockAgentApi } from "./support/mock-agent-api";
+
+test.beforeEach(async ({ page }) => {
+  await mockAgentApi(page, {
+    sessions: [
+      {
+        session_id: "browser-history-session",
+        title: "城南供水压力复核",
+        created_at: "2026-07-21T09:30:00+08:00",
+        updated_at: "2026-07-21T10:35:00+08:00",
+        run_status: "completed"
+      }
+    ]
+  });
+});
 
 type BoundingBox = {
   x: number;
@@ -12,9 +27,7 @@ async function waitForAnimations(locator: Locator) {
     const animations = element
       .getAnimations({ subtree: true })
       .filter((animation) => animation.effect?.getTiming().iterations !== Infinity);
-    await Promise.all(
-      animations.map((animation) => animation.finished.catch(() => undefined))
-    );
+    await Promise.all(animations.map((animation) => animation.finished.catch(() => undefined)));
   });
 }
 
@@ -103,9 +116,7 @@ async function expectIntegratedHeader(header: Locator) {
   expect(composition.borderRadius).toBe("0px");
 }
 
-test("desktop Agent header expands into one attached acrylic history surface", async ({
-  page
-}) => {
+test("desktop Agent header expands into one attached acrylic history surface", async ({ page }) => {
   await page.goto("/", { waitUntil: "domcontentloaded" });
 
   const agentPanel = page.locator('aside[aria-label="Agent 命令面板"]');
@@ -194,16 +205,12 @@ test("desktop Agent header expands into one attached acrylic history surface", a
   await expect(history).toBeHidden();
 });
 
-test("mobile Agent mirrors the desktop floating history surface", async ({
-  page
-}) => {
+test("mobile Agent mirrors the desktop floating history surface", async ({ page }) => {
   await page.setViewportSize({ width: 390, height: 844 });
   await page.goto("/", { waitUntil: "domcontentloaded" });
   await page.getByRole("button", { name: "打开 Agent 面板" }).click();
 
-  const agentPanel = page
-    .locator('aside[aria-label="Agent 命令面板"]')
-    .filter({ visible: true });
+  const agentPanel = page.locator('aside[aria-label="Agent 命令面板"]').filter({ visible: true });
   await expect(agentPanel).toBeVisible();
   await waitForAnimations(agentPanel);
   const mobileSheet = page.getByRole("region", { name: "Agent 工作台抽屉" });