feat: vendor and censor the phishing blocklist at build time (closes #219)

The blocklist URL in shipped code named a competitor and pointed at a moving
ref, and the extension re-fetched from it every 24 hours, which also meant a
third party decided what this wallet warns about. All of that is gone.

script/vendor-blocklist fetches upstream at a pinned commit, verifies the
sha256 of the bytes that commit serves, and writes
src/shared/phishingBlocklist.json. It is build-time tooling, never shipped, and
the one place in the repo that names the upstream project; a source reference
nobody can verify is not a source reference.

The artifact stores truncated sha256 digests rather than domain names. That is
what censors it: the previous file contained the competitor's name 6,475 times,
as phishing domains impersonating them, and not one of those domains is
dropped. It also makes lookups a binary search over a fixed-width string, so
nothing is built at module load — which matters on MV3, where the worker
re-evaluates the module on every wake — and takes the file from 8.7 MB to
1.7 MB.

script/check-censored enforces the rest: it reads the name out of the vendoring
script rather than repeating it, and fails on any occurrence in the working
tree or under dist/ that is not one of the three literals shipped code cannot
avoid — two provider-shim identifiers in src/content/inpage.js and one ERC-20's
on-chain name in src/shared/tokenList.js. Each is permitted only at the path
that carries it, and at the emitted paths that path is bundled into, so a
literal appearing anywhere else fails like any other occurrence. It runs in
make check, which inspects dist/ when there is one and says loudly when there
is not, and again with --require-dist at the end of every make build.

Removing the runtime fetch retires the delta, the extension-storage persistence
and the 24-hour alarm from #158. A retired alarm is now cleared rather than
left waking the worker forever on installs that already have it.

The e2e suite drives the warning end to end from a real blocklisted origin
served as a real http(s) site, with a control asserting the banner stays hidden
for one that is not listed. Its service-worker interception canary needed a new
anchor, since the startup fetch it used to watch for no longer happens: it now
wakes the worker with a message and asks it for one throwaway fetch.

LICENSE no longer cites a repository that returns 404.

eslint.config.js gains one block: script/lib/ holds node programs the shell
entrypoints call, and without it they lint with no globals at all.

script/vendor-blocklist

@@ -0,0 +1,105 @@
+#!/bin/sh
+# script/vendor-blocklist: refresh the vendored phishing blocklist at
+# src/shared/phishingBlocklist.json from its upstream source. Our own extension
+# to scripts-to-rule-them-all.
+#
+# This is build-time repo tooling and is not shipped. It is the one place in
+# this repo that names the upstream project, because a source reference that
+# does not say what the source is cannot be verified by anyone; the artifact it
+# writes carries no names at all (see src/shared/domainHash.js).
+# script/check-censored reads the name back out of this file rather than
+# repeating it, so it stays defined exactly once.
+#
+# Run it deliberately, not on every build: the output is committed, and the
+# extension does no runtime fetching, so the shipped list is exactly as fresh as
+# the last time someone ran this and landed the result. Re-run it, land the
+# diff, cut a release; that is the whole refresh path.
+#
+# Pinned by content hash, twice over, as REPO_POLICIES.md requires. The commit
+# below is an immutable ref — the upstream default branch moves several times a
+# day and cannot be pinned — and UPSTREAM_SHA256 is the sha256 of the bytes that
+# commit serves. A mismatch is a hard failure: a vendoring step that accepts
+# whatever it is handed is a supply-chain hole, and this one feeds a security
+# warning shown to users.
+#
+# To move the pin: pick the new commit, run this with the new UPSTREAM_COMMIT
+# and an UPSTREAM_SHA256 you have not yet updated, and it will print the hash it
+# actually got. Verify that hash against the source independently before
+# recording it. Never copy the "actual" line in on trust.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+# Upstream, pinned 2026-08-17.
+UPSTREAM_ORG="MetaMask"
+UPSTREAM_REPO="eth-phishing-detect"
+UPSTREAM_COMMIT="6dddf74a87da3e1a0841f7ae0d1cb31aaf2c05db"
+UPSTREAM_FILE="src/config.json"
+UPSTREAM_SHA256="166d5b3504e8f4ed52eae37d3dd20c1a56efa0502bfb3dc957044ff8b5f1283f"
+
+OUTPUT="src/shared/phishingBlocklist.json"
+
+WORK=""
+
+cleanup() {
+    [ -z "$WORK" ] || rm -rf "$WORK"
+}
+trap cleanup EXIT INT TERM
+
+fail() {
+    echo "vendor-blocklist: $*" >&2
+    exit 1
+}
+
+sha256_of() {
+    if command -v sha256sum >/dev/null 2>&1; then
+        sha256sum "$1" | cut -d' ' -f1
+    elif command -v shasum >/dev/null 2>&1; then
+        shasum -a 256 "$1" | cut -d' ' -f1
+    else
+        fail "neither sha256sum nor shasum is available, so the fetched
+    source cannot be verified. Refusing to vendor unverified content."
+    fi
+}
+
+main() {
+    cd "$ROOT"
+
+    command -v curl >/dev/null 2>&1 ||
+        fail "curl is required to fetch the upstream list"
+    command -v node >/dev/null 2>&1 ||
+        fail "node is required to build the artifact; run script/bootstrap"
+
+    WORK="$(mktemp -d "${TMPDIR:-/tmp}/autistmask-vendor-blocklist.XXXXXX")" ||
+        fail "could not create a working directory"
+
+    url="https://raw.githubusercontent.com/$UPSTREAM_ORG/$UPSTREAM_REPO/$UPSTREAM_COMMIT/$UPSTREAM_FILE"
+    echo "Fetching $url"
+    curl -fsSL --proto '=https' --tlsv1.2 -o "$WORK/source.json" "$url" ||
+        fail "the fetch failed, so nothing was vendored"
+
+    actual="$(sha256_of "$WORK/source.json")"
+    if [ "$actual" != "$UPSTREAM_SHA256" ]; then
+        fail "sha256 mismatch on the fetched source.
+    expected: $UPSTREAM_SHA256
+    actual:   $actual
+    The pinned commit is immutable, so the same commit serving different bytes
+    means the content was substituted somewhere between upstream and here.
+    Nothing was written. Do not update the expectation to match unless you have
+    verified the new bytes independently."
+    fi
+    echo "Verified sha256 $actual"
+
+    node script/lib/build-blocklist.js "$WORK/source.json" "$WORK/out.json" ||
+        fail "the transform failed, so nothing was written"
+
+    if [ -f "$OUTPUT" ] && cmp -s "$WORK/out.json" "$OUTPUT"; then
+        echo "vendor-blocklist: $OUTPUT is already up to date"
+        return 0
+    fi
+
+    cp "$WORK/out.json" "$OUTPUT"
+    echo "vendor-blocklist: wrote $OUTPUT (sha256 $(sha256_of "$OUTPUT"))"
+}
+
+main "$@"