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

The shared files are the sneak/prompts copies at dd4027b, with this
repository's own entries after them. make lint and make test each build
one phase of the Dockerfile without the cache, and each covers the
frontend through a node stage; the builder stage waits on both and takes
its version from git describe unless VERSION is given. golangci-lint
moves to v2.14.0 with the new .golangci.yml, and one test spells
X-Request-ID as canonicalheader asks. prettier formats only JavaScript,
CSS, HTML and Markdown, so the shared .golangci.yml stays as fetched.
script/fmt and script/fmt-check put ~/.local/bin on PATH, which the
shared workflow no longer does.

Model: opus-5-5

script/test

@@ -1,17 +1,19 @@
 #!/bin/sh
-# script/test: run the test suite for the whole repo: the frontend at
-# the repo root, then the Go backend in backend/. Each half has its own
-# 30-second limit, and there is none around both: from a cold Go build
-# cache, compiling the backend's tests with the race detector can take
-# 30 seconds on its own, and Go's -timeout leaves the compile out.
+# script/test: run the test suite. Testing is a phase of the Dockerfile
+# and this builds that phase alone, on the same terms as script/lint:
+# --target because a phase that is not the last stage is built only when
+# named, --no-cache because a cached test layer is a test that did not
+# run, and a tag so each build replaces the previous image.
 set -eu
 
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    script/frontend-test
-    backend/script/test
+    docker build --no-cache \
+        --target test \
+        -t "$("$SCRIPT_DIR/projectname")-test" .
 }
 
 main "$@"