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

Runs the real popup in a pinned containerized Chrome and fails on any uncaught
page error or console.error. Also fixes the two defects it caught: the missing
showView import in addToken.js and the missing addressDotHtml import in
transactionDetail.js.

closes #150
closes #151

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 +84,66 @@ 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.
+
+That reporting has one bound worth knowing. Observation ends when the browser
+context is torn down, and nothing can watch traffic after that, so the run keeps
+collecting for a fixed grace period after the last test returns
+(`TRAILING_WATCH_MS` in `tests/e2e/run.js`, currently 1500ms) and then closes
+the context. A request whose _first_ dispatch falls after that window is never
+seen at all and cannot fail the run. In practice a request a test fires without
+awaiting reaches the route handler about 10ms later, and anything on a repeating
+timer gets observed on an earlier tick during the ~20s suite — but a one-shot
+call deliberately deferred past the window will escape.
+
+That interception covers the MV3 background service worker as well as the popup
+page, which it does not by default — `script/test-e2e` sets
+`PW_EXPERIMENTAL_SERVICE_WORKER_NETWORK_EVENTS=1` for it. Because that flag is
+experimental, the harness does not take it on trust. At launch it waits for the
+background worker's **own** startup request — the phishing blocklist fetch that
+`src/background/index.js` issues unconditionally — to arrive in the route
+handler, and aborts the entire suite if none does within 30 seconds
+(`tests/e2e/harness.js`). The check is passive on purpose: a synthetic probe
+fetched from inside the worker via `worker.evaluate()` was tried first and
+rejected, because evaluating in an extension service worker that early kills the
+worker outright, destroying the thing being measured. Observing traffic the
+extension already generates perturbs nothing. Losing the race fails closed — the
+suite refuses to run rather than passing quietly.
+
+As defence in depth, Chrome is also started with
+`--host-resolver-rules=MAP * ~NOTFOUND`, so a request that ever did slip past
+the route handler could not resolve a host at all. That only bounds the damage;
+detecting escaping traffic remains the canary's job. To see what is actually
+being intercepted, run with `E2E_TRACE_NETWORK=1` and every routed request is
+printed, tagged `[sw]` or `[page]`.
+
+**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