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.

README.md

@@ -73,6 +73,8 @@ provide:
   git pre-commit hook
 - `script/projectname` — print the project name (used for the Docker image tag)
 - `script/test` — run the test suite (jest)
+- `script/test-e2e` — run the browser end-to-end suite (docker required; see
+  [End-to-End Tests](#end-to-end-tests))
 - `script/lint` — run the linter
 - `script/fmt` — format all files (writes)
 - `script/fmt-check` — check formatting (read-only)
@@ -82,6 +84,35 @@ provide:
 - `script/precommit` — run by the git pre-commit hook; runs `script/check`
 - `script/install-precommit` — install the git pre-commit hook
 
+## End-to-End Tests
+
+`make test-e2e` builds `dist/chrome/` and drives the **real popup in a real
+Chrome**, loaded as an unpacked MV3 extension inside a pinned
+`mcr.microsoft.com/playwright` container (pinned by digest in `script/test-e2e`;
+docker is required and the suite fails loudly rather than skipping if it is
+unavailable). The suite lives in `tests/e2e/` and is driven by
+`playwright-core`, whose version must stay matched to the container's Playwright
+version — the browsers ship inside the image.
+
+It covers popup load, wallet creation through the UI, the Add Token screen and
+the transaction detail screen for an ERC-20 transfer. All outbound network is
+intercepted at the browser level and served from fixtures in
+`tests/e2e/network.js`, so the run is deterministic and fully offline;
+unrecognised outbound requests are reported as failures rather than silently
+allowed.
+
+**Any uncaught page error or `console.error` fails the run.** That is the point:
+a `ReferenceError` from a used-but-not-imported identifier is invisible to
+`make check` (`script/lint` is only `prettier --check`) but fatal in a browser,
+and this suite exists because exactly that class of bug shipped twice.
+
+`make test-e2e` is deliberately **not** part of `make check` or `make test`.
+`REPO_POLICIES.md` caps `make test` at 20 seconds and a browser suite does not
+fit; nothing in `tests/e2e/` is named `*.test.js`, so jest cannot pick it up
+either. It is also not wired into the Gitea workflow yet — docker-in-docker in
+CI is a separate question. Run it locally before changing anything under
+`src/popup/views/`.
+
 ## Rationale
 
 Common popular EVM wallets have become bloated with swap UIs, portfolio