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 Dockerfile phase without the cache, both covering 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; 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, which the shared workflow no
longer does. 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/check

@@ -1,6 +1,8 @@
 #!/bin/sh
 # script/check: run all checks (test, lint, fmt-check). Our own
-# extension to scripts-to-rule-them-all. Must not modify any files.
+# extension to scripts-to-rule-them-all. test and lint are Docker
+# phases; fmt-check is native, because a formatter writes the working
+# tree. Must not modify any files.
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"