Re-vendor the shared files from sneak/prompts at dd4027b (closes #113)

The shared files are the sneak/prompts copies at dd4027b, plus this
repository's own entries. make lint and make test each build one
Dockerfile phase without the cache, both covering the frontend; the
builder stage waits on both and takes its version from git describe
unless VERSION is given. The test phase keeps Go's module and build
caches in memory, out of the image make test tags. golangci-lint moves
to v2.14.0 with the new .golangci.yml; one test spells X-Request-ID as
canonicalheader asks. prettier formats only JavaScript, CSS, HTML and
Markdown, so .golangci.yml stays as fetched. script/fmt and
script/fmt-check put ~/.local/bin on PATH. script/bootstrap keeps a Go
only if it is exactly GO_VERSION, and re-checks the go on PATH after
installing.

Model: opus-5-5

script/lint

@@ -1,23 +1,23 @@
 #!/bin/sh
-# script/lint: lint the whole repo: eslint over the frontend, then the Go
-# linter over backend/.
+# 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.
 #
-# No linter runs on the host: this builds the frontend-lint and lint
-# stages of Dockerfile, the digest-pinned node and golangci-lint images.
-# The first runs eslint; the second runs the backend's fmt-check and
-# lint targets. --no-cache makes each linter really run every time
-# rather than reuse an earlier result, and each stage is built for its
-# checks alone, so no image is kept.
+# 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 "$ROOT"
-    timeout 300 docker build --no-cache --target frontend-lint \
-        --output type=cacheonly .
-    timeout 300 docker build --no-cache --target lint \
-        --output type=cacheonly .
+    docker build --no-cache \
+        --target lint \
+        -t "$("$SCRIPT_DIR/projectname")-lint" .
 }
 
 main "$@"