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

backend/script/test

@@ -1,18 +1,21 @@
 #!/bin/sh
-# script/test: run the backend test suite with the race detector and
-# coverage. Go's own -timeout bounds the tests and not their compile,
-# so a cold build cache cannot fail it. The race detector needs cgo,
-# and so a C compiler. If the tests fail, they run again with -v for
-# the details, and the script fails even if that run passes.
+# script/test: run the backend test suite on the host with the race
+# detector and coverage. The root make test runs the same in the test
+# phase of the root Dockerfile. Go's own -timeout bounds the tests and
+# not their compile, so a cold build cache cannot fail it. -count=1
+# keeps Go's test result cache out of both runs, so neither can report
+# a stored pass. The race detector needs cgo, and so a C compiler. If
+# the tests fail, they run again with -v for the details, and the
+# script fails even if that run passes.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    go test -timeout 30s -race -cover ./... || {
+    go test -count=1 -timeout 90s -race -cover ./... || {
         echo "--- Rerunning with -v for details ---"
-        go test -timeout 30s -race -v ./...
+        go test -count=1 -timeout 90s -race -v ./...
         exit 1
     }
 }