test: containerized Chrome end-to-end harness that drives the real popup (closes #181)

`make check` was green while the AddToken screen crashed on every open.
`script/lint` is only `prettier --check`, so a used-but-not-imported
identifier is invisible until a browser evaluates it. This adds a suite
that runs the real popup in a real Chrome and treats any uncaught page
error or console.error as a failure.

- `script/test-e2e` (with `make test-e2e` as a thin shim) builds
  `dist/chrome/` and runs `tests/e2e/run.js` inside the Playwright image,
  pinned by digest. `playwright-core` is pinned to the matching 1.56.0
  through `yarn.lock`; the two must be bumped together because the
  browsers ship inside the image.
- Deliberately outside `script/test` and `script/check`: REPO_POLICIES
  caps `make test` at 20 seconds. Nothing under `tests/e2e/` is named
  `*.test.js`, so jest cannot pick it up either.
- Launches with `channel: "chromium"`; the default headless shell
  silently refuses to load extensions with no error at all. The extension
  id is read from the service worker URL, never hardcoded.
- All http(s) traffic is intercepted at the browser level and served from
  fixtures, so the run is deterministic and offline. Unrecognised
  outbound requests are reported as failures rather than allowed.
- A missing build or an unavailable container fails loudly; a skip that
  looks like a pass is the failure mode this is meant to prevent.
- One allowlisted page error, for the libsodium WASM CSP fallback tracked
  as #182, which is otherwise untouched here.

The suite was demonstrated failing against the unfixed tree with
`pageerror: showView is not defined` and `pageerror: addressDotHtml is
not defined`, so it carries the two one-line import fixes it caught:

closes #150 — `showView` restored to the destructure in
`src/popup/views/addToken.js`, dropped by a22f33d, which made the
AddToken screen unreachable and corrupted the navigation stack.

closes #151 — `addressDotHtml` restored in
`src/popup/views/transactionDetail.js`, dropped by df031fd, which threw
before `showView("transaction")` for every ERC-20 transfer. The shared
`renderAddressHtml` helper is not used here on purpose: it hardcodes the
`/address/` explorer URL, and this row needs the token-specific `/token/`
link.

tests/e2e/harness.js

@@ -0,0 +1,188 @@
+// End-to-end harness: launches a real Chromium with the unpacked MV3
+// build loaded, collects every uncaught page error and console.error, and
+// exposes the popup flows the tests drive.
+//
+// This runs inside the pinned Playwright container; see script/test-e2e.
+// It is deliberately NOT part of make check — REPO_POLICIES.md caps
+// make test at 20 seconds and a browser suite does not fit.
+
+"use strict";
+
+const fs = require("fs");
+const os = require("os");
+const path = require("path");
+
+const { chromium } = require("playwright-core");
+const { installNetworkStubs } = require("./network");
+
+const REPO_ROOT = path.resolve(__dirname, "..", "..");
+const EXT_PATH = path.join(REPO_ROOT, "dist", "chrome");
+
+// Page errors that are known, tracked, and deliberately tolerated. Every
+// entry must name the issue that will remove it. This list is the one
+// concession in an otherwise zero-tolerance policy: an uncaught error is
+// how this harness caught issue #150 in the first place.
+const ALLOWED_ERRORS = [
+    {
+        // libsodium ships a WASM build and an asm.js fallback. The
+        // extension CSP (script-src 'self', with no wasm-unsafe-eval)
+        // refuses the WASM module on every popup load; libsodium catches
+        // it and falls back to asm.js, so the wallet works. Deciding
+        // which backend actually ships is issue #182, and this entry gets
+        // deleted when that lands.
+        issue: "#182",
+        pattern: /Refused to compile or instantiate WebAssembly module/,
+    },
+];
+
+function isAllowed(text) {
+    return ALLOWED_ERRORS.some((a) => a.pattern.test(text));
+}
+
+class ErrorCollector {
+    constructor() {
+        this.entries = [];
+    }
+
+    record(kind, text) {
+        const line = kind + ": " + String(text).split("\n")[0];
+        if (isAllowed(line)) return;
+        this.entries.push(line);
+    }
+
+    mark() {
+        return this.entries.length;
+    }
+
+    since(mark) {
+        return this.entries.slice(mark);
+    }
+}
+
+function attachErrorListeners(ctx, errors) {
+    const attachPage = (page) => {
+        page.on("pageerror", (err) => {
+            errors.record("pageerror", err.message || String(err));
+        });
+        page.on("console", (msg) => {
+            if (msg.type() === "error") {
+                errors.record("console.error", msg.text());
+            }
+        });
+    };
+    ctx.pages().forEach(attachPage);
+    ctx.on("page", attachPage);
+    // Per-page listeners only: the context-level "weberror" event covers
+    // the same page exceptions and would double-report them. Playwright
+    // exposes no error event for service workers, so an uncaught error in
+    // the background worker is not visible here — everything this suite
+    // drives lives in the popup page.
+}
+
+// The extension id is derived from the unpacked path, so it changes and
+// must never be hardcoded. It is the host part of the service worker URL.
+async function extensionId(ctx) {
+    let [sw] = ctx.serviceWorkers();
+    if (!sw) {
+        sw = await ctx.waitForEvent("serviceworker", { timeout: 30000 });
+    }
+    return new URL(sw.url()).host;
+}
+
+async function launch(routeOpts) {
+    if (!fs.existsSync(path.join(EXT_PATH, "manifest.json"))) {
+        throw new Error(
+            "no unpacked build at " +
+                EXT_PATH +
+                " — run make build before the e2e suite",
+        );
+    }
+
+    const userDir = fs.mkdtempSync(path.join(os.tmpdir(), "autistmask-e2e-"));
+    const ctx = await chromium.launchPersistentContext(userDir, {
+        // channel: "chromium" is load-bearing. The default headless mode
+        // uses the headless shell, which silently refuses to load
+        // extensions: there is no error at all, the service worker simply
+        // never appears. This cost real debugging time once already.
+        channel: "chromium",
+        headless: true,
+        args: [
+            "--disable-extensions-except=" + EXT_PATH,
+            "--load-extension=" + EXT_PATH,
+            // The container runs unprivileged; Chrome's sandbox needs
+            // capabilities the harness deliberately does not grant it.
+            "--no-sandbox",
+        ],
+    });
+
+    const errors = new ErrorCollector();
+    attachErrorListeners(ctx, errors);
+    routeOpts.report = (text) => errors.record("network", text);
+    await installNetworkStubs(ctx, routeOpts);
+
+    const id = await extensionId(ctx);
+    const popupUrl = "chrome-extension://" + id + "/src/popup/index.html";
+
+    return {
+        ctx,
+        errors,
+        extensionId: id,
+        popupUrl,
+        async close() {
+            await ctx.close();
+            fs.rmSync(userDir, { recursive: true, force: true });
+        },
+    };
+}
+
+// ---------------------------------------------------------------- flows
+
+const PASSWORD = "e2e-harness-password";
+
+async function visible(page, selector, timeout = 15000) {
+    await page.waitForSelector(selector, { state: "visible", timeout });
+}
+
+async function openPopup(ctx, popupUrl) {
+    const page = await ctx.newPage();
+    await page.goto(popupUrl);
+    return page;
+}
+
+// Full wallet creation through the real UI: BIP-39 generation, libsodium
+// vault encryption and extension storage persistence, for real.
+async function createWallet(page) {
+    await page.click("#btn-welcome-add");
+    await visible(page, "#view-add-wallet");
+    await page.click("#btn-generate-phrase");
+    await page.waitForFunction(() => {
+        const el = document.getElementById("wallet-mnemonic");
+        return el && el.value.trim().split(/\s+/).length >= 12;
+    });
+    await page.fill("#add-wallet-password", PASSWORD);
+    await page.fill("#add-wallet-password-confirm", PASSWORD);
+    await page.click("#btn-add-wallet-confirm");
+    await visible(page, "#view-main", 60000);
+}
+
+// Reach the address detail screen from wherever the popup restored to.
+// Clicking .address-row does not open it; the [info] button does.
+async function openAddressDetail(page) {
+    const onAddress = await page.isVisible("#view-address");
+    if (!onAddress) {
+        await visible(page, "#view-main");
+        await page.click("#wallet-list .btn-addr-info");
+    }
+    await visible(page, "#view-address");
+}
+
+module.exports = {
+    ALLOWED_ERRORS,
+    EXT_PATH,
+    REPO_ROOT,
+    createWallet,
+    launch,
+    openAddressDetail,
+    openPopup,
+    visible,
+};