Re-vendor the shared files from sneak/prompts at dd4027b (closes #504)

Fetches the shared files unchanged from sneak/prompts commit dd4027b and
adds .prettierignore. .gitignore, .editorconfig and .dockerignore keep
this repository's own entries after the shared content: its Go, database
and asset entries, tabs for *.go, and its anchored host artifacts and
database patterns.

Linting moves into the Dockerfile's lint phase on the golangci-lint
v2.14.0 image, which also runs the js-lint stage, and Dockerfile.lint is
gone. Tests move into a test phase on the golang bookworm image.
script/lint, test, docker and cibuild are the model scripts, every docker
build in script/ passes --no-cache, and the .ci-fingerprint barrier is
gone. The workflow no longer calls script/ci-mark-superseded, so it and
its tests are removed. make build passes -trimpath and -s -w.

Model: opus-5-5

script/bootstrap

@@ -11,7 +11,6 @@ ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 PKGMGR=""
 SUDO=""
-APT_UPDATED=""
 
 detect_pkgmgr() {
     [ -n "$PKGMGR" ] && return 0
@@ -40,14 +39,7 @@ pkg_install() {
     detect_pkgmgr
     case "$PKGMGR" in
         nix) nix-env -iA "nixpkgs.$1" ;;
-        apt)
-            # Package lists may be empty (fresh images); refresh once per run.
-            if [ -z "$APT_UPDATED" ]; then
-                $SUDO env DEBIAN_FRONTEND=noninteractive apt-get update
-                APT_UPDATED=1
-            fi
-            $SUDO env DEBIAN_FRONTEND=noninteractive apt-get install -y "$2"
-            ;;
+        apt) $SUDO env DEBIAN_FRONTEND=noninteractive apt-get install -y "$2" ;;
         brew) brew install "$3" ;;
         apk) apk add --no-cache "$4" ;;
     esac