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

Makefile

@@ -1,5 +1,5 @@
 .PHONY: bootstrap setup dev build test lint fmt fmt-check check \
-	add-dependency tidy frontend-check frontend-viewport-test docker hooks
+	add-dependency tidy frontend-viewport-test docker hooks
 
 # Standard targets are thin shims; the implementations live in script/
 # per the scripts-to-rule-them-all pattern (see the Entrypoints section
@@ -42,14 +42,8 @@ add-dependency:
 tidy:
 	@script/tidy
 
-# The frontend tests and format check, for Dockerfile's frontend stage,
-# which has neither Go nor Docker. Use check everywhere else.
-frontend-check:
-	@script/frontend-check
-
 # Responsive-layout verification in a containerised browser. Kept out of
-# check: it needs Docker and takes minutes, where make test has to stay
-# under 20 seconds.
+# check: it takes minutes.
 frontend-viewport-test:
 	@script/frontend-viewport-test