chore: re-vendor canonical files from prompts at dd4027b (closes #472)

Copies .dockerignore, .gitignore, .prettierignore, check.yml and
REPO_POLICIES.md from sneak/prompts at dd4027b. The repo's own entries
(dist/, release/, yarn files) are kept after the canonical content.

The Dockerfile gets separate lint and test phases. Its last stage
depends on both, checks the git describe version and runs make build.
script/lint, test, check, cibuild and docker are the canonical models.
check-censored moves into the lint phase and test-verify-build into the
test phase. fmt and fmt-check fall back to the nvm-installed node. The
e2e image builds are uncached. Comments that cited the old 20-second
test cap now say 60.

Model: opus-5-5

script/test-e2e

@@ -4,7 +4,7 @@
 # scripts-to-rule-them-all.
 #
 # Deliberately NOT called by script/check or script/test: REPO_POLICIES.md
-# caps make test at 20 seconds and a browser suite does not fit. Run it
+# caps make test at 60 seconds and a browser suite does not fit. Run it
 # yourself before touching popup views. ESLint's no-undef now catches a
 # used-but-not-imported identifier in make check, but only this suite sees
 # what a view actually does when it runs.
@@ -45,7 +45,10 @@ main() {
     trap 'cleanup; exit 130' INT TERM
 
     echo "Building the Chrome e2e image (extension included)..."
-    docker build --iidfile "$IIDFILE" -t "$IMAGE" -f tests/e2e/Dockerfile .
+    # --no-cache: the image build runs make build and its checks, and a
+    # cached layer is a check that did not run.
+    docker build --no-cache --iidfile "$IIDFILE" -t "$IMAGE" \
+        -f tests/e2e/Dockerfile .
 
     echo "Running e2e suite in the pinned Playwright container..."
     # The image is run by ID, not by tag: where two clones of this repo run