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

script/lint

@@ -1,51 +1,23 @@
 #!/bin/sh
-# script/lint: run the linter (eslint, then prettier --check).
+# script/lint: run the linter. Linting is a phase of the Dockerfile and
+# this builds that phase alone; the linter is never installed or run on
+# a developer host, where a shared result cache and a host-global lock
+# make its answer untrustworthy.
 #
-# Linting is containerized. ESLint results depend on the ESLint version, and
-# the pinned one is the one in the image; a host's own install must not be
-# able to decide whether this repo is green. From a host this therefore builds
-# the Dockerfile's `lint` stage, which runs this same script inside the image.
-#
-# AUTISTMASK_LINT_NATIVE is set only in that image (see the Dockerfile) and is
-# what stops the recursion, so `make check` inside the CI build lints in place
-# instead of trying to reach a docker daemon it does not have.
+# The phase is not the last stage in the file, so it is built only when
+# --target names it. --no-cache because a cached lint layer is a lint
+# that did not run. The tag makes each build replace the previous image
+# instead of leaving a dangling one behind.
 set -eu
 
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-
-    case "${AUTISTMASK_LINT_NATIVE:-}" in
-    1)
-        echo "Linting..."
-        yarn run lint 2>&1
-        return 0
-        ;;
-    "") ;;
-    *)
-        # Set but not recognized: say so rather than silently taking the
-        # docker path, which would look like the variable had no effect.
-        echo "lint: AUTISTMASK_LINT_NATIVE is set to" \
-            "'${AUTISTMASK_LINT_NATIVE}'; the only recognized value is 1" >&2
-        exit 1
-        ;;
-    esac
-
-    if ! command -v docker >/dev/null 2>&1; then
-        echo "lint: docker is required; linting does not run on the host" >&2
-        exit 1
-    fi
-
-    echo "Linting in the pinned container..."
-    # --progress=plain: the default progress renderer collapses the lint
-    # output on success, and a lint run whose output cannot be seen is not
-    # evidence that it ran.
-    #
-    # --output=type=cacheonly: the exit status is the whole result; exporting
-    # an image afterwards costs about ten times the lint itself.
-    docker build --progress=plain --target lint \
-        --output=type=cacheonly . 2>&1
+    docker build --no-cache \
+        --target lint \
+        -t "$("$SCRIPT_DIR/projectname")-lint" .
 }
 
 main "$@"