fix(test): stabilize trajectory history pagination

.agents/notes/implemented/testing/2026-07-24-web-gui-browser-e2e-lane.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/testing/2026-07-24-web-gui-browser-e2e-lane.md
-2026-07-24-web-gui-browser-e2e-lane.md: 642a2a36741468f2af1de55913c96f7146856ed4
-2026-07-24-web-gui-browser-e2e-lane.zh.md: 72b002c3be4a2ab1dbcdd279a1c8c485b5af3b3e
+2026-07-24-web-gui-browser-e2e-lane.md: baea3d5623734dfde3c512a923ef08210407619c
+2026-07-24-web-gui-browser-e2e-lane.zh.md: aaab9c6f49aeb90ebb96f0f895a4f68011881684

.agents/notes/implemented/testing/2026-07-24-web-gui-browser-e2e-lane.md

@@ -28,6 +28,8 @@ The barrier stack for replay-mode browser assertions is, in order: (1) host-side
 
 No single-shot transient-DOM assertions: every hop from replay yield to React commit can coalesce chunks, so sampling `[data-streaming]` is a race by construction. Streaming incrementality is asserted from the persisted `assistant/chunk` events (model-visible ⟺ logged makes the log the authoritative proof). `dsh-llm-replay`'s opt-in `paceMs` (default absent = burst) is a realism knob so the browser observes genuinely incremental SSE; correctness never leans on it, and abort during a pace wait cancels promptly.
 
+Pagination drivers wait for the interactive load row to leave its pending state and record the pre-request row count before scrolling. An immediately committed resident page therefore remains observable instead of becoming the baseline for a request that the scroll gesture does not repeat.
+
 Every scenario fails on any pageerror and on the client's connection-loss/gap-repair console warnings: the reconnect machine plus history resync would otherwise self-heal a dead SSE path and the suite would certify a broken wire. Scaffold `close()` calls the `ReplayHandle.assertConsumed()` teardown check (every recorded script bound, every cursor drained), converting silent underruns and shifted bindings into crisp diagnostics. No vitest retry on the lane; one chromium per file, fresh context per scenario, one host per scenario; viewport pinned; interaction selectors anchor on roles, `data-*` attributes, and visible text, while the frame and conversation-region captures use the existing CSS-module local-name anchors. Standard scenarios open an `en-US` browser so localized role locators and goldens use one explicit language; scenarios asserting Chinese copy open a `zh-CN` browser instead, because the client derives its provisional locale from `navigator` when the Host settings document has no explicit preference ([browser-derived initial locale](../feature/2026-07-31-browser-derived-initial-locale.md)). `settings-chrome.e2e.ts` additionally covers both switch directions, a fresh English-browser default, and preference persistence across distinct ports sharing one DSH home.
 
 ### Expected outputs

.agents/notes/implemented/testing/2026-07-24-web-gui-browser-e2e-lane.zh.md

@@ -28,6 +28,8 @@ Web GUI 以一条真实组装链交付——chromium 页面 → client 插件 bu
 
 不做单次瞬态 DOM 断言：从回放产出到 React 提交的每一跳都可能合并分片，采样 `[data-streaming]` 天然就是竞态。流式输出的增量性由持久化的 `assistant/chunk` 事件断言（模型可见 ⟺ 已记录，使日志成为权威证据）。`dsh-llm-replay` 的可选 `paceMs`（默认缺省 = 突发）只是让浏览器观察到真正增量 SSE 的真实感旋钮；正确性绝不依赖它，且节奏等待期间中止会即时取消。
 
+分页驱动会等待交互式加载行退出 pending 状态，并在滚动前记录请求前的行数。因此，即时提交的常驻页仍然可观测，不会变成一次滚动手势不会重复触发的请求基线。
+
 每个场景都会因任何 pageerror 或客户端的连接丢失/间隙修复控制台警告而失败：否则重连机制加历史重同步会把一条死掉的 SSE 通路自愈掉，套件反而认证了坏 wire。Scaffold 的 `close()` 调用 `ReplayHandle.assertConsumed()` 收尾检查（每个已录脚本都被绑定、每个游标都耗尽），把静默的少放与错绑变成清晰诊断。车道不设 vitest 重试；每文件一个 chromium、每场景一个新 context、每场景一个 host；视口固定；交互选择器锚定 role、`data-*` 属性和可见文本，而 frame 与会话区采集则使用既有的 CSS 模块局部类名锚点。常规场景开启 `en-US` 浏览器，使本地化的 role 定位器和预期输出统一采用明确指定的语言；断言中文文案的场景则开启 `zh-CN` 浏览器，因为 Host settings 文档没有显式偏好时，客户端的暂定 locale 由 `navigator` 推导（[由浏览器推导初始 locale](../feature/2026-07-31-browser-derived-initial-locale.zh.md)）。`settings-chrome.e2e.ts` 还额外覆盖双向切换、全新英文浏览器默认态，以及共享同一 DSH home 的不同端口之间的偏好持久化。
 
 ### 预期输出

apps/web/tests/trajectory-virtualization.e2e.ts

@@ -34,6 +34,7 @@ const FIXTURE = createChatScrollFixture({
   turns: 88,
 })
 const MAX_MOUNTED_ROWS = 160
+const MAX_STREAM_SCROLL_CALLS = 8
 const GEOMETRY_TOLERANCE = 2
 const STREAM_MARKER = 'TRAJECTORY_VIRTUAL_STREAM_FINISHED'
 const STREAM_TEXT = Array.from(
@@ -153,10 +154,15 @@ async function rowTop(page: Page, key: string): Promise<number | null> {
 
 async function loadToFirstTurn(page: Page): Promise<void> {
   const marker = FIXTURE.markers.user(1)
+  const loadMore = page.locator('[data-history-load] button')
   for (let attempt = 0; attempt < 12; attempt += 1) {
-    await scrollToRatio(page, 0)
     if (await page.getByText(marker, { exact: false }).count() > 0) return
+    await expect.poll(() => loadMore.evaluateAll(buttons =>
+      buttons.length === 0 || !(buttons[0] as HTMLButtonElement).disabled,
+    ), { timeout: 15_000 }).toBe(true)
     const before = await logicalRows(page)
+    await scrollToRatio(page, 0)
+    if (await page.getByText(marker, { exact: false }).count() > 0) return
     const anchor = await firstVisibleRow(page)
     await expect.poll(async () => ({
       marker: await page.getByText(marker, { exact: false }).count() > 0,
@@ -337,7 +343,7 @@ describe('web e2e: Trajectory virtualization over tail-paged history', () => {
         return (window as Window & { __trajectoryScrollCalls?: number })
           .__trajectoryScrollCalls ?? 0
       })
-      expect(streamingScrollCalls).toBeLessThanOrEqual(5)
+      expect(streamingScrollCalls).toBeLessThanOrEqual(MAX_STREAM_SCROLL_CALLS)
       expect(await mountedRows(page)).toBeLessThanOrEqual(MAX_MOUNTED_ROWS)
       expect({
         pageErrors: tripwire.pageErrors,