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, keeping the repo's own
entries (dist/, release/, yarn files) 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 citing the old test caps or what
runs a script are updated.

Model: opus-5-5

Dockerfile

@@ -1,41 +1,80 @@
+# Lint phase: ESLint, prettier --check, and script/check-censored. The tools
+# are invoked directly rather than through `make lint` or `script/lint`, which
+# are themselves a docker build and would recurse into a daemon that does not
+# exist in a build step.
+#
 # node:22-slim (22.x LTS), 2026-02-24
-FROM node@sha256:5373f1906319b3a1f291da5d102f4ce5c77ccbe29eb637f072b6c7b70443fc36 AS base
+FROM node@sha256:5373f1906319b3a1f291da5d102f4ce5c77ccbe29eb637f072b6c7b70443fc36 AS lint
 
 WORKDIR /app
 
-# Marks "already inside the lint container" for script/lint, which otherwise
-# shells out to docker to build the lint stage below. Nothing outside this
-# image sets it.
-ENV AUTISTMASK_LINT_NATIVE=1
-
-# script/test's default 30s bound is the host figure. In here the same suite
-# starts on a cold jest cache and shares the runner with the rest of the build,
-# so 30s is too tight — it killed a healthy suite at 30.6s on a cold CI cache.
-# 180s still catches a hang in three minutes and cannot be tripped by a suite
-# that is merely running on contended hardware.
-ENV AUTISTMASK_TEST_TIMEOUT=180
-
-# script/bootstrap installs all prerequisites (make via apt here; node
-# is already in the base image, yarn comes via corepack) and runs
-# yarn install --frozen-lockfile. Dependency manifests are copied first
-# so the bootstrap layer is cached until they change.
 COPY script/ script/
 COPY package.json yarn.lock ./
 RUN script/bootstrap
 
 COPY . .
 
-# Lint stage — fail fast on static analysis and formatting, before the tests
-# and the build. This is also the stage script/lint builds from a host, which
-# is how linting stays on the pinned ESLint rather than the host's.
-FROM base AS lint
-RUN make lint
+RUN yarn run lint
+RUN script/check-censored
+
+# Test phase, same shape and for the same reason: the jest suite (its worker
+# cap is in package.json), rerun verbose on failure, then
+# script/test-verify-build.
+#
+# node:22-slim (22.x LTS), 2026-02-24
+FROM node@sha256:5373f1906319b3a1f291da5d102f4ce5c77ccbe29eb637f072b6c7b70443fc36 AS test
+
+WORKDIR /app
+
+COPY script/ script/
+COPY package.json yarn.lock ./
+RUN script/bootstrap
+
+COPY . .
+
+RUN timeout 90 yarn run test || \
+    { echo "--- Rerunning with --verbose for details ---"; \
+      timeout 90 yarn run test:verbose; exit 1; }
+RUN script/test-verify-build
+
+# Development environment with the extension built, and the last stage: a
+# plain `docker build .` names no target and so builds this one. Nothing is
+# wanted from the two phases above; the copies are what make BuildKit build
+# them first, so this image cannot be produced unless lint and test passed. A
+# stage appended after this one would drop all three out of a plain build.
+#
+# node:22-slim (22.x LTS), 2026-02-24
+FROM node@sha256:5373f1906319b3a1f291da5d102f4ce5c77ccbe29eb637f072b6c7b70443fc36
+
+WORKDIR /app
 
-# Full check and build. The COPY --from is a no-op file copy whose only job is
-# to make BuildKit finish the lint stage before this one starts; without it the
-# stages run in parallel and a lint failure would not fail the build early.
-FROM base AS check
 COPY --from=lint /app/package.json /dev/null
+COPY --from=test /app/package.json /dev/null
 
-RUN make check
-RUN make build
+# script/bootstrap installs all prerequisites, git included. Manifests are
+# copied first so that layer stays cached until dependencies change.
+COPY script/ script/
+COPY package.json yarn.lock ./
+RUN script/bootstrap
+# A tar-stream context keeps the sender's file owners, which git refuses.
+RUN git config --system --add safe.directory /app
+
+COPY . .
+
+# The VERSION build arg when one is given, otherwise
+# `git describe --tags --always` on the .git in the build context. With .git
+# present, a version that is still empty, dev or unknown fails the build: git
+# is missing or could not read the checkout, and build.js, which stamps the
+# extension with the commit it was built from, would stamp "unknown".
+ARG VERSION
+RUN VERSION="${VERSION:-$(git describe --tags --always)}"; \
+    if [ -e .git ]; then \
+        case "$VERSION" in ""|dev|unknown) \
+            echo "version is '$VERSION' although .git is present" >&2; \
+            exit 1 ;; \
+        esac; \
+    fi; \
+    make build
+# A LABEL cannot run git, so it carries the build argument alone; a plain
+# `docker build .` leaves it empty.
+LABEL org.opencontainers.image.version="${VERSION}"