feat(desktop)!: give the Renderer the transcript window

apps/desktop/.gitignore

@@ -1,5 +1,9 @@
 # Playwright E2E run artifacts: traces, videos, screenshots, last-run state.
 test-results/
+# Throwaway drivers written beside the suite while investigating a scenario by
+# hand. They resolve `@playwright/test` from here, which is why they live in the
+# tree at all, and they are nobody's to keep.
+e2e/.scratch/
 resources/workers/
 .maka-dev/
 .maka-dev.staging/

apps/desktop/e2e-budget.json

@@ -66,8 +66,8 @@
       "electron": "observation seeding, reconnect and settle are Host subscriptions surviving a renderer remount"
     },
     "transcript-scroll-cost.spec.ts": {
-      "tests": 3,
-      "electron": "the perf budget is measured from CDP wheel input and the browser's own render skipping"
+      "tests": 4,
+      "electron": "the perf budget is measured from CDP wheel input and the browser's own render skipping, and reader displacement only exists against a real layout"
     },
     "workhub-layout.spec.ts": {
       "tests": 2,

apps/desktop/e2e/partial-history-notice.spec.ts

@@ -19,66 +19,51 @@
 
 import { expect, test } from './fixtures';
 
-const GAP = '.maka-transcript-gap-row';
 const TURN = '.maka-transcript-turn';
+/** Turns the partial-history fixture seeds. */
+const PARTIAL_HISTORY_TURN_COUNT = 18;
 
-test('bounded transcript ranges expose only their truthful boundary gaps', async ({
+test('a bounded transcript range reaches its whole history without a control to ask', async ({
   partialHistoryWindow: page,
 }) => {
   await page.setViewportSize({ width: 1_400, height: 800 });
 
-  const olderGap = page.locator('[data-transcript-gap="older"]');
-  const newerGap = page.locator('[data-transcript-gap="newer"]');
-  await expect(olderGap).toBeVisible();
-  await expect(olderGap.getByRole('button', {
-    name: /^(?:加载较早消息|Load earlier messages)$/,
-  })).toBeVisible();
-  await expect(newerGap).toHaveCount(0);
-  await expect(page.locator('.maka-transcript-history-controls')).toHaveCount(0);
+  await expect(page.locator(TURN).first()).toBeVisible();
+  expect(await page.locator(TURN).count()).toBeLessThan(PARTIAL_HISTORY_TURN_COUNT);
 
   const oldestPrompt = page.locator(
     '.maka-prompt-rail-tick[data-prompt-turn-id="turn-partial-history-1"]',
   );
   await expect(oldestPrompt).toBeVisible();
   await oldestPrompt.click();
 
-  const firstTurn = page.locator('[data-turn-id="turn-partial-history-1"]');
-  await expect(firstTurn).toBeVisible();
-  await expect(firstTurn).toHaveAttribute('data-search-highlight', 'true');
-  await expect(olderGap).toHaveCount(0);
-  await expect(newerGap).toBeVisible();
-  await expect(newerGap.getByRole('button', {
-    name: /^(?:加载较新消息|Load newer messages)$/,
-  })).toBeVisible();
-  await expect(page.locator(GAP)).toHaveCount(1);
-  expect(await page.locator(TURN).count()).toBeLessThanOrEqual(10);
+  await expect(page.locator('[data-turn-id="turn-partial-history-1"]')).toBeVisible();
+  // Where the jump landed, read from the reading position rather than from
+  // `data-search-highlight`: that highlight clears itself 2.2s after the
+  // command lands, so waiting for the Turn to mount and then asserting it
+  // fails whenever loading the page around it takes longer than the flash —
+  // measured here as a 3s pass turning into an 18s timeout under load.
+  await expect(oldestPrompt).toHaveAttribute('data-active', 'true');
+  // A jump lands on its own page, not on the whole history.
+  expect(await page.locator(TURN).count()).toBeLessThan(PARTIAL_HISTORY_TURN_COUNT);
 
-  const loadNewer = newerGap.getByRole('button', {
-    name: /^(?:加载较新消息|Load newer messages)$/,
-  });
-  await loadNewer.click();
-  await expect(page.locator('[data-turn-id="turn-partial-history-2"]')).toBeVisible();
-  await expect(olderGap).toHaveCount(0);
-  await expect(newerGap).toBeVisible();
-  await expect(loadNewer).toBeEnabled();
-
-  await loadNewer.click();
-  await expect(page.locator('[data-turn-id="turn-partial-history-3"]')).toBeVisible();
-  await expect(olderGap).toBeVisible();
-  await expect(newerGap).toBeVisible();
-  await expect(loadNewer).toBeEnabled();
-  await expect(oldestPrompt).toBeVisible();
-  await expect(page.locator(GAP)).toHaveCount(2);
-  expect(await page.locator(TURN).count()).toBeLessThanOrEqual(10);
+  // The newer side of the jump fills on its own as the reader moves into it.
+  await page.mouse.move(700, 400);
+  await expect(async () => {
+    await page.mouse.wheel(0, 400);
+    await expect(page.locator('[data-turn-id="turn-partial-history-3"]')).toBeVisible();
+  }).toPass({ timeout: 30_000 });
 
   const returnToLatest = page.getByRole('button', {
     name: /^(?:滚动主对话到底部|Scroll main conversation to bottom)$/,
   });
   await expect(returnToLatest).toBeVisible();
   await returnToLatest.click();
 
-  await expect(page.locator('[data-turn-id="turn-partial-history-18"]')).toBeVisible();
-  await expect(newerGap).toHaveCount(0);
+  // Reading the tail page and rebuilding the window around it is slower than
+  // the paging above, and measured past the suite's 10s expect timeout here.
+  await expect(page.locator(`[data-turn-id="turn-partial-history-${PARTIAL_HISTORY_TURN_COUNT}"]`))
+    .toBeVisible({ timeout: 30_000 });
   await expect(oldestPrompt).toBeVisible();
-  expect(await page.locator(TURN).count()).toBeLessThanOrEqual(10);
+  expect(await page.locator(TURN).count()).toBeLessThan(PARTIAL_HISTORY_TURN_COUNT);
 });