Move the e2e suites into the repo (tests/), out of /tmp

The browser harness lived in /tmp/opencode and an overnight reboot
wiped it. It now lives in tests/ and survives reboots, is versioned
and runs with one command.

- tests/lib.mjs: shared helpers (Chromium auto-detect, seeding,
  IndexedDB fixtures, stub/extra instance spawn with process-group
  cleanup, check/finish).
- tests/run-all.mjs + npm run test:e2e [filter]: runs the ten suites
  in order with a summary; suites that need a stub Ollama or VAPID
  keys start their own next start instance on 3208/3209, verify the
  port is free and kill the group on exit. Test scratch in
  tests/.tmp/ (gitignored).
- Suites rebuilt and green against the current build: regression 38,
  mobile 94 (tab matrix, ... sheet, settings sheet, axe), wizard 83,
  native 31 (PWA/offline/share/back/undo/haptics/draft), i18n 13,
  freeze-loading 6, review 15, phase1 36 (backup/sync/usage limits),
  phase2 42 (learning engine/reminders), phase3 21 (homework check).
  379 checks, 10/10 suites in one full run.
- playwright-core + axe-core added as devDependencies; CHROME env or
  the newest ~/.cache/ms-playwright chromium is used.
- README: new decision 45 documenting the harness; decision 44's
  verification note updated.

The older suites' exact sources were lost with the wipe, so the
rebuilt versions reconstruct the same feature areas rather than
being byte-identical.

tests/freeze-loading-test.mjs

@@ -0,0 +1,45 @@
+/**
+ * Freeze loading screen: it must appear the moment generation starts, keep
+ * the wizard's action bar out of the way, and Cancel must return to the
+ * wizard with the cancelled notice (not a stuck spinner).
+ */
+import { BASE, launchBrowser, makeChecker, makePage, seed } from "./lib.mjs";
+
+const { check, finish } = makeChecker();
+const browser = await launchBrowser();
+const { context, page } = await makePage(browser);
+await seed(page, { decks: [] });
+
+// Hold the generation so the loading screen stays up.
+await page.route("**/api/generate", () => new Promise(() => {}));
+await page.goto(`${BASE}/create`, { waitUntil: "networkidle" });
+await page.waitForTimeout(800);
+await page.getByRole("button", { name: "Paste text instead" }).click();
+await page.locator("textarea").first().fill("Photosynthesis needs light and water.");
+await page.getByRole("button", { name: "Next" }).click();
+await page.waitForTimeout(300);
+await page.getByRole("button", { name: "Next" }).click();
+await page.waitForTimeout(300);
+
+const tClick = Date.now();
+await page.getByRole("button", { name: "Freeze my deck" }).click();
+let appeared = true;
+await page
+  .locator('img[src="/icons/icon-512.png"]')
+  .waitFor({ state: "visible", timeout: 2000 })
+  .catch(() => {
+    appeared = false;
+  });
+check("loading screen appears immediately after Freeze", appeared, `${Date.now() - tClick} ms`);
+check("stage message visible", await page.getByText(/Reading your notes|Finding the key ideas/).first().isVisible().catch(() => false));
+check("cancel available", await page.getByRole("button", { name: "Cancel" }).isVisible().catch(() => false));
+check("wizard bar is gone", (await page.locator("[data-wizard-bar]").count()) === 0);
+
+await page.getByRole("button", { name: "Cancel" }).click();
+await page.waitForTimeout(700);
+check("cancel returns to the wizard", (await page.locator("[data-wizard-bar]").count()) === 1);
+check("cancel shows the notice + retry", await page.getByRole("button", { name: "Retry" }).isVisible());
+
+await context.close();
+await browser.close();
+finish();