Re-vendor the canonical files from sneak/prompts at dd4027b (closes #95)

The shared files are the copies at sneak/prompts commit dd4027b, with this
repository's own entries kept after them. script/lint, script/test and
REPO_POLICIES.md come from its next at c55a0cb, so the lint and test
builds write no image. golangci-lint is v2.14.0 and raises no findings.
Lint and test are phases of the Dockerfile; the tests run under the race
detector as nobody, so Dockerfile.lint, script/verify-lint-image-pin and
make test-race are gone. Every docker build in script/ passes --no-cache.
Formatting runs on the host: script/bootstrap installs the pinned node and
yarn, and the prettier and markdown stages are gone. .claude/settings.json
is deleted.

Deviation: the workflow keeps fetch-depth: 0.
Deviation: .gitignore keeps the scan database patterns.
Over the cap: make test takes 82 to 100 seconds on this host.

Model: opus-5-5

TODO.md

@@ -29,6 +29,17 @@
 
 # Completed Steps
 
+- re-vendor the canonical files from `sneak/prompts` commit `dd4027b`, with
+  `script/lint`, `script/test` and `REPO_POLICIES.md` from its `next` at
+  `c55a0cb`: golangci-lint v2.14.0; lint and test are phases of the `Dockerfile`
+  that write no image, and `make test` runs the suite under the race detector,
+  so `Dockerfile.lint`, `script/verify-lint-image-pin` and `make test-race` are
+  gone; every `docker build` in `script/` passes `--no-cache`; prettier runs on
+  the host, from the node and yarn `script/bootstrap` installs, so the
+  `prettier` and `markdown` stages are gone and the build stage installs `git`
+  and `make` itself; `.claude/settings.json` is deleted (2026-10-08,
+  https://git.eeqj.de/sneak/sfdupes/issues/95)
+
 - cut the narration from `TODO.md` Completed Steps and from the comments in
   `script/` and both Dockerfiles; §Workflow now branches from and merges to
   `next` (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/49)
@@ -37,12 +48,15 @@
   container, outside `make check` (2026-10-04,
   https://git.eeqj.de/sneak/sfdupes/issues/18)
 
-- a bare `docker build .` fails with a message naming `script/cibuild` and
-  `script/docker` instead of serving the gates from cache (2026-10-04,
-  https://git.eeqj.de/sneak/sfdupes/issues/39)
+- a bare `docker build .` failed, naming `script/cibuild` and `script/docker`,
+  rather than serve the gates from cache (2026-10-04,
+  https://git.eeqj.de/sneak/sfdupes/issues/39). Since
+  https://git.eeqj.de/sneak/sfdupes/issues/95 a bare build succeeds, as
+  `REPO_POLICIES.md` requires, and may serve the gates from cache; the builds in
+  `script/` pass `--no-cache`, so theirs always run
 
-- `make fmt` and `make fmt-check` run prettier over all Markdown, in Docker, and
-  CI checks it; all Markdown reformatted (2026-10-04,
+- `make fmt` and `make fmt-check` run prettier over all Markdown, and CI checks
+  it; all Markdown reformatted (2026-10-04,
   https://git.eeqj.de/sneak/sfdupes/issues/19)
 
 - `script/lint` writes no image, so a run no longer leaves an untagged one
@@ -167,32 +181,28 @@
   `ENV PATH=/home/builder/go/bin:$PATH` went with its `go install`.
   `script/verify-linter-pin` is retired; `script/verify-lint-image-pin`, a gate
   in both files, compares their two `FROM` lines and restates neither pin.
-  Traps: an unchanged tree lets a lint build pass in under a second having run
-  no linter, so every gate `RUN` references `ARG CHECK_EPOCH` (BuildKit hashes
-  the expanded command) and `script/lint` passes `"$(date +%s)-$$"`, the PID
-  because two runs land in the same second easily. Nothing inside an image build
-  may shell out to docker, so the `Dockerfile` lint stage calls `golangci-lint`
-  directly and the build stage runs `make test` and `make fmt-check` instead of
-  `make check`, through `make` because the Makefile's `export CGO_ENABLED = 0`
-  only reaches what it invokes. `COPY --from=lint /src/go.sum /dev/null`
-  replaces the copied linter binary as the only edge making the build stage wait
-  for lint; dropping it would end fail-fast linting under a still-green build.
-  `golangci-lint config verify`, included per the ruling, validates from an
-  embedded schema with no network call, but `go mod download` above the gates
-  still needs the network on a cold cache. Verified: `make lint` green with no
-  `golangci-lint` on `PATH`; two back-to-back `script/lint` runs on an untouched
-  tree both ran the linter (27.7s and 28.7s in the lint step, `COPY . .`
-  `CACHED` above); a planted unused variable failed `script/lint`, and failed
-  `make docker` at `[lint 9/9]` with the build stage stopped at
-  `[builder 3/12]`; the drift guard fails on a tag-only, a digest-only and an
-  unreadable reference, naming both sides; under `--network none` config verify
-  passes a valid config and rejects an invalid one; `make docker` green in 5m35s
-  with all six gates run under one epoch (lint 37.6s, test 25.2s reporting
-  `ok sneak.berlin/go/sfdupes 1.938s coverage: 88.5%`, not `(cached)`); in the
-  builder image with the Go test cache off, `--user 0:0` still fails
-  `TestScanHardlinkRunFailsTogether` where the unprivileged user passes. Noted
-  for follow-up, not fixed here: `golangci-lint` warns that `gomodguard` is
-  deprecated since v2.12.0 in favour of `gomodguard_v2`.
+  Traps: nothing inside an image build may shell out to docker, so the
+  `Dockerfile` lint stage calls `golangci-lint` directly and the build stage
+  runs `make test` and `make fmt-check` instead of `make check`, through `make`
+  because the Makefile's `export CGO_ENABLED = 0` only reaches what it invokes.
+  `COPY --from=lint /src/go.sum /dev/null` replaces the copied linter binary as
+  the only edge making the build stage wait for lint; dropping it would end
+  fail-fast linting under a still-green build. `golangci-lint config verify`,
+  included per the ruling, validates from an embedded schema with no network
+  call, but `go mod download` above the gates still needs the network on a cold
+  cache. Verified: `make lint` green with no `golangci-lint` on `PATH`; two
+  back-to-back `script/lint` runs on an untouched tree both ran the linter
+  (27.7s and 28.7s in the lint step, `COPY . .` `CACHED` above); a planted
+  unused variable failed `script/lint`, and failed `make docker` at `[lint 9/9]`
+  with the build stage stopped at `[builder 3/12]`; the drift guard fails on a
+  tag-only, a digest-only and an unreadable reference, naming both sides; under
+  `--network none` config verify passes a valid config and rejects an invalid
+  one; `make docker` green in 5m35s with all six gates run (lint 37.6s, test
+  25.2s reporting `ok sneak.berlin/go/sfdupes 1.938s coverage: 88.5%`, not
+  `(cached)`); in the builder image with the Go test cache off, `--user 0:0`
+  still fails `TestScanHardlinkRunFailsTogether` where the unprivileged user
+  passes. Noted for follow-up, not fixed here: `golangci-lint` warns that
+  `gomodguard` is deprecated since v2.12.0 in favour of `gomodguard_v2`.
 
 - install the Docker build stage's prerequisites by running `script/bootstrap`
   instead of `apk add --no-cache make` inline (2026-08-09, branch
@@ -205,43 +215,32 @@
   `script/verify-linter-pin`, run in the build stage before bootstrap, fails the
   build naming both versions unless that copied binary is the version
   `script/bootstrap` pins; a pin it cannot read is a hard failure, not a skip.
-  `$GOPATH/bin` joins `PATH`, where bootstrap's `go install` lands. Everything
-  added sits above `ARG CHECK_EPOCH`, and the `chown` and `USER builder` still
-  precede `make check`. Verified: the guard fails the build with both versions
-  named when the lint stage's linter is faked to another version, and passes an
-  unmodified build; bootstrap runs clean under Alpine's `sh` and `apk`, finding
-  the copied linter already at the pin; a second build served the bootstrap and
-  dependency layers `CACHED` while both gates ran with a fresh epoch; a planted
-  `unused` finding failed the build at the lint gate in 48.9s with the build
-  stage's `make check` never starting; and the suite run in the image as
-  `--user 0:0` fails `TestScanHardlinkRunFailsTogether`, so the drop to the
-  unprivileged user is still needed. That last check needs the Go test cache
-  off: as root it first reported `ok ... (cached)`, reusing the build-time
-  result. Build times on a noisy shared host: 2m13s on an unchanged tree, 2m17s
-  and 4m29s after a source change, 5m14s cold, which breaches the policy
-  ceiling; `chown -R builder:builder /src /home/builder` walks the module cache
-  and alone varied from 77s to 210s across those builds, and `main` measured
-  5m03s cold with a 209s `chown`. Filed as
+  `$GOPATH/bin` joins `PATH`, where bootstrap's `go install` lands. The `chown`
+  and `USER builder` still precede `make check`. Verified: the guard fails the
+  build with both versions named when the lint stage's linter is faked to
+  another version, and passes an unmodified build; bootstrap runs clean under
+  Alpine's `sh` and `apk`, finding the copied linter already at the pin; a
+  second build served the bootstrap and dependency layers `CACHED` while both
+  gates ran; a planted `unused` finding failed the build at the lint gate in
+  48.9s with the build stage's `make check` never starting; and the suite run in
+  the image as `--user 0:0` fails `TestScanHardlinkRunFailsTogether`, so the
+  drop to the unprivileged user is still needed. That last check needs the Go
+  test cache off: as root it first reported `ok ... (cached)`, reusing the
+  build-time result. Build times on a noisy shared host: 2m13s on an unchanged
+  tree, 2m17s and 4m29s after a source change, 5m14s cold, which breaches the
+  policy ceiling; `chown -R builder:builder /src /home/builder` walks the module
+  cache and alone varied from 77s to 210s across those builds, and `main`
+  measured 5m03s cold with a 209s `chown`. Filed as
   https://git.eeqj.de/sneak/sfdupes/issues/43
 - bust the Docker layer cache for the gate steps, so `script/cibuild` and
   `script/docker` cannot report a green they did not earn (2026-08-09, branch
   `cibuild-cache-bust`, closes https://git.eeqj.de/sneak/sfdupes/issues/32): the
   `Dockerfile` copies the tree before its gates, so on an unchanged tree Docker
-  served them from cache and the build exited 0 having run nothing. Both scripts
-  now pass `--build-arg CHECK_EPOCH="$(date +%s)"`. `ARG` is per stage and the
-  gates span two stages, so it is declared in both; BuildKit hashes the expanded
-  command, so each gate `RUN` echoes the epoch, which also logs it as evidence
-  the layer ran. It sits below the dependency layers so they stay cached.
-  Verified under `BUILDKIT_PROGRESS=plain`, each script run twice back to back
-  on an unchanged tree: all three gates ran on all four runs with a fresh epoch
-  (`script/cibuild` 78.8s then 61.1s; `script/docker` 61.1s then 53.4s), and
-  thirteen steps were still served `CACHED`. With a planted `unused` finding the
-  build failed at `make lint` in 36.1s and the build-stage `make check` never
-  started. Run as root, the same image fails `TestScanHardlinkRunFailsTogether`,
-  because root reads through the `chmod(0)` the test relies on, so the build
-  stage must drop to the unprivileged `builder` user. Local fix only;
-  propagating it to the canonical templates is
-  https://git.eeqj.de/sneak/prompts/issues/26
+  served them from cache and the build exited 0 having run nothing. Every
+  `docker build` in `script/` now passes `--no-cache` instead
+  (https://git.eeqj.de/sneak/sfdupes/issues/95). Run as root, the tests fail
+  `TestScanHardlinkRunFailsTogether`, because root reads through the `chmod(0)`
+  the test relies on, so they run as an unprivileged user
 - check the installed golangci-lint version in `script/bootstrap` instead of
   only its presence (2026-08-09, branch `bootstrap-version-check`, closes
   https://git.eeqj.de/sneak/sfdupes/issues/24): the version lives only in
@@ -397,6 +396,3 @@ Accepted divergences (no action):
 
 - flat single-package layout with `.go` files in the repo root — fine for a
   small single-binary tool per the Go styleguide; the tracker audit agrees
-- `make test` runs without `-race` — the repo mandates `CGO_ENABLED=0` (pure-Go
-  builds) and the race detector requires cgo, so the detector runs in a separate
-  cgo-enabled container, `make test-race`, which is not part of `make check`