build: unify the gate so root make check covers the backend (closes #16)

Root make check, and with it the pre-commit hook, now gates the Go
backend too. The backend's Makefile targets are shims over
backend/script/*; script/cibuild builds both images and is the
workflow's only build step. Root make test runs both halves within one
30-second timeout.

Root make lint runs golangci-lint only in Docker, by building the lint
stage of Dockerfile.backend without the cache; the .golangci.yml drift
check moved into backend/script/lint. script/bootstrap installs no
linter: it reuses a Go at least as new as backend/go.mod asks for,
otherwise installs the pinned, hash-verified release, linked into
~/.local/bin without replacing anything it did not create. With VERSION
unset or empty, the backend version falls back to git describe inside a
git checkout, then to dev.

Model: opus-5-5

script/bootstrap

@@ -5,7 +5,18 @@
 # or apk (detected in that order); assumes nothing is present. Node is
 # used directly if installed; otherwise it is installed at a pinned
 # version via nvm (installing nvm itself first, from a hash-verified
-# release archive, never curl | sh).
+# release archive, never curl | sh). Go, with its gofmt, is used
+# directly if it is at least the version backend/go.mod asks for;
+# otherwise the pinned Go release is installed from its hash-verified
+# archive.
+#
+# What this script installs outside the system package manager lives
+# under $HOME and is linked into ~/.local/bin, where make and the git
+# hook find it once that directory is on PATH. Nothing in ~/.local/bin
+# that this script did not create is ever replaced.
+#
+# golangci-lint is not installed: make lint runs it in Docker, which
+# this script does not install either.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
@@ -16,6 +27,12 @@ NVM_VERSION="0.40.3"
 # sha256 of https://github.com/nvm-sh/nvm/archive/refs/tags/v0.40.3.tar.gz
 NVM_SHA256="5f4d6aaa04a177dc93c985e31dbc411ab6b8c6e1e21d8015dbc1372625fcd1d0"
 YARN_VERSION="1.22.22"
+# The Go inside the golang:1.25-alpine image Dockerfile.backend builds
+# with, 2026-08-09. The archive hashes are in ensure_go.
+GO_VERSION="1.25.7"
+
+BIN_DIR="$HOME/.local/bin"
+TOOLCHAIN="$HOME/.local/share/$("$ROOT/script/projectname")/toolchain"
 
 PKGMGR=""
 SUDO=""
@@ -79,6 +96,26 @@ verify_sha256() {
     fi
 }
 
+# link_bin <target> <name>: make an installed tool reachable as
+# $BIN_DIR/<name>. Only a symlink this script made, one pointing into
+# $TOOLCHAIN or ~/.nvm, is ever replaced; if anything else is already
+# there, bootstrap stops.
+link_bin() {
+    link="$BIN_DIR/$2"
+    if [ -L "$link" ] || [ -e "$link" ]; then
+        case "$(readlink "$link" || true)" in
+            "$TOOLCHAIN"/* | "$HOME"/.nvm/*) ;;
+            *)
+                echo "bootstrap: $link was not created by this script;" >&2
+                echo "  remove or rename it, then re-run bootstrap" >&2
+                exit 1
+                ;;
+        esac
+    fi
+    mkdir -p "$BIN_DIR"
+    ln -sf "$1" "$link"
+}
+
 # nvm is a bash script; run a command in a bash with nvm loaded
 nvm_sh() {
     bash -c ". \"\$HOME/.nvm/nvm.sh\" && $*"
@@ -103,39 +140,117 @@ ensure_node() {
     if ! missing node; then return 0; fi
     ensure_nvm
     nvm_sh "nvm install $NODE_VERSION"
+    link_bin "$HOME/.nvm/versions/node/v$NODE_VERSION/bin/node" node
 }
 
+# ensure_yarn: corepack writes its shims (pnpm and yarnpkg as well as
+# yarn) into $TOOLCHAIN rather than next to itself, and the npm fallback
+# installs there too; only yarn is linked.
 ensure_yarn() {
     if ! missing yarn; then return 0; fi
+    shims="$TOOLCHAIN/corepack-shims"
+    mkdir -p "$shims"
     if ! missing corepack; then
-        corepack enable
+        corepack enable --install-directory "$shims"
         corepack prepare "yarn@$YARN_VERSION" --activate
     elif [ -s "$HOME/.nvm/nvm.sh" ]; then
-        nvm_sh "nvm use $NODE_VERSION >/dev/null && corepack enable && \
+        nvm_sh "nvm use $NODE_VERSION >/dev/null && \
+            corepack enable --install-directory \"$shims\" && \
             corepack prepare yarn@$YARN_VERSION --activate"
     else
-        npm install -g "yarn@$YARN_VERSION"
+        npm install -g --prefix "$TOOLCHAIN/npm-global" "yarn@$YARN_VERSION"
+        shims="$TOOLCHAIN/npm-global/bin"
     fi
+    link_bin "$shims/yarn" yarn
 }
 
-install_js_deps() {
-    if missing yarn && [ -s "$HOME/.nvm/nvm.sh" ]; then
-        nvm_sh "nvm use $NODE_VERSION >/dev/null && cd \"$ROOT\" && \
-            yarn install --frozen-lockfile"
-    else
-        yarn install --frozen-lockfile
+# go_ok: the go on PATH has its gofmt beside it (a Go release ships the
+# two together) and is at least the version backend/go.mod asks for.
+# GOTOOLCHAIN=local makes an older go fail here instead of fetching a
+# newer toolchain for itself.
+go_ok() {
+    if missing go; then return 1; fi
+    [ -x "$(dirname "$(command -v go)")/gofmt" ] || return 1
+    (cd "$ROOT/backend" && GOTOOLCHAIN=local go list -m >/dev/null 2>&1)
+}
+
+# ensure_go: unless go_ok, install GO_VERSION and link its go and gofmt.
+# They are linked on every run that needs them, so a deleted link is put
+# back, and the archive is unpacked again if either binary is missing.
+ensure_go() {
+    if go_ok; then return 0; fi
+    go_dir="$TOOLCHAIN/go-$GO_VERSION"
+    if [ ! -x "$go_dir/bin/go" ] || [ ! -x "$go_dir/bin/gofmt" ]; then
+        # sha256 of each archive, from https://go.dev/dl/?mode=json
+        case "$(uname -s)-$(uname -m)" in
+            Linux-x86_64)
+                plat="linux-amd64"
+                sha="12e6d6a191091ae27dc31f6efc630e3a3b8ba409baf3573d955b196fdf086005"
+                ;;
+            Linux-aarch64)
+                plat="linux-arm64"
+                sha="ba611a53534135a81067240eff9508cd7e256c560edd5d8c2fef54f083c07129"
+                ;;
+            Darwin-x86_64)
+                plat="darwin-amd64"
+                sha="bf5050a2152f4053837b886e8d9640c829dbacbc3370f913351eb0904cb706f5"
+                ;;
+            Darwin-arm64)
+                plat="darwin-arm64"
+                sha="ff18369ffad05c57d5bed888b660b31385f3c913670a83ef557cdfd98ea9ae1b"
+                ;;
+            *)
+                echo "bootstrap: no pinned Go release for this platform" >&2
+                exit 1
+                ;;
+        esac
+        if missing curl; then pkg_install curl curl curl curl; fi
+        mkdir -p "$TOOLCHAIN"
+        curl -fsSL -o "$go_dir.tar.gz" \
+            "https://go.dev/dl/go$GO_VERSION.$plat.tar.gz"
+        verify_sha256 "$go_dir.tar.gz" "$sha"
+        # Unpacked beside its final place and then moved there, so an
+        # interrupted run never leaves a partial Go that looks complete.
+        rm -rf "$go_dir.partial"
+        mkdir "$go_dir.partial"
+        tar -xzf "$go_dir.tar.gz" -C "$go_dir.partial" --strip-components=1
+        rm -rf "$go_dir" "$go_dir.tar.gz"
+        mv "$go_dir.partial" "$go_dir"
     fi
+    link_bin "$go_dir/bin/go" go
+    link_bin "$go_dir/bin/gofmt" gofmt
 }
 
 main() {
     cd "$ROOT"
 
+    # Tools linked on an earlier run count as installed, and tools linked
+    # on this run are found by the steps after it.
+    path_hint=""
+    case ":$PATH:" in
+        *":$BIN_DIR:"*) ;;
+        *) path_hint=yes ;;
+    esac
+    PATH="$BIN_DIR:$PATH"
+
     if missing make; then pkg_install gnumake make make make; fi
     if missing git; then pkg_install git git git git; fi
 
     ensure_node
     ensure_yarn
-    install_js_deps
+    yarn install --frozen-lockfile
+
+    ensure_go
+    (cd "$ROOT/backend" && go mod download)
+
+    if missing docker; then
+        echo "bootstrap: docker not found; make lint, and so make check" >&2
+        echo "  and the pre-commit hook, need it to run the Go linter" >&2
+    fi
+    if [ -n "$path_hint" ] && [ -d "$BIN_DIR" ]; then
+        echo "bootstrap: add $BIN_DIR to the front of your PATH, e.g." >&2
+        echo "  export PATH=\"\$HOME/.local/bin:\$PATH\"" >&2
+    fi
 
     echo "bootstrap complete"
 }

script/cibuild

@@ -1,13 +1,17 @@
 #!/bin/sh
-# script/cibuild: run the CI build. The Dockerfile runs make check, so
-# a successful build implies all checks pass.
+# script/cibuild: run the CI build. It builds both images: the frontend
+# from Dockerfile and the backend from Dockerfile.backend. Each runs its
+# half of the checks as build steps, so a successful cibuild implies the
+# whole repo is green. This is the only build step the Gitea workflow
+# runs.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    docker build .
+    timeout 300 docker build .
+    timeout 300 docker build -f Dockerfile.backend .
 }
 
 main "$@"

script/docker

@@ -1,6 +1,7 @@
 #!/bin/sh
-# script/docker: build the Docker image tagged with the project name.
-# The tag comes from script/projectname.
+# script/docker: build both Docker images, tagged with the project name
+# from script/projectname: the frontend as <name>, from Dockerfile, and
+# the backend as <name>-server, from Dockerfile.backend.
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -8,7 +9,9 @@ ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    timeout 300 docker build -t "$("$SCRIPT_DIR/projectname")" .
+    name="$("$SCRIPT_DIR/projectname")"
+    timeout 300 docker build -t "$name" .
+    timeout 300 docker build -t "$name-server" -f Dockerfile.backend .
 }
 
 main "$@"

script/fmt

@@ -1,12 +1,14 @@
 #!/bin/sh
-# script/fmt: format all files (writes).
+# script/fmt: format the whole repo (writes): prettier over everything
+# it understands, then gofmt over the Go backend.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    yarn prettier --write .
+    "$ROOT/script/frontend-fmt"
+    "$ROOT/backend/script/fmt"
 }
 
 main "$@"

script/fmt-check

@@ -1,13 +1,14 @@
 #!/bin/sh
-# script/fmt-check: check formatting (read-only). Same scope as
-# script/fmt, but fails instead of writing.
+# script/fmt-check: check formatting across the whole repo (read-only).
+# Same scope as script/fmt, but fails instead of writing.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    yarn prettier --check .
+    "$ROOT/script/frontend-fmt-check"
+    "$ROOT/backend/script/fmt-check"
 }
 
 main "$@"

script/frontend-check

@@ -0,0 +1,18 @@
+#!/bin/sh
+# script/frontend-check: run the frontend half of the checks only (test,
+# lint, fmt-check). This exists for the frontend Dockerfile, whose build
+# stage is a node image with neither Go nor Docker; the backend half is
+# gated by Dockerfile.backend. Everywhere else, use script/check, which
+# covers the whole repo. Must not modify any files.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    "$ROOT/script/frontend-test"
+    "$ROOT/script/frontend-lint"
+    "$ROOT/script/frontend-fmt-check"
+}
+
+main "$@"

script/frontend-fmt

@@ -0,0 +1,14 @@
+#!/bin/sh
+# script/frontend-fmt: format the frontend and every other file prettier
+# understands, repo-wide (writes). backend/ is in .prettierignore; Go
+# sources are formatted by backend/script/fmt.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    yarn prettier --write .
+}
+
+main "$@"

script/frontend-fmt-check

@@ -0,0 +1,13 @@
+#!/bin/sh
+# script/frontend-fmt-check: check prettier formatting (read-only). Same
+# scope as script/frontend-fmt, but fails instead of writing.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    yarn prettier --check .
+}
+
+main "$@"

script/frontend-lint

@@ -0,0 +1,12 @@
+#!/bin/sh
+# script/frontend-lint: run the frontend linter (prettier in check mode).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    yarn prettier --check .
+}
+
+main "$@"

script/frontend-test

@@ -0,0 +1,14 @@
+#!/bin/sh
+# script/frontend-test: run the frontend test suite. The frontend has no
+# unit tests; the production build serves as the test (fails on broken
+# code).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    timeout 30 yarn build
+}
+
+main "$@"

script/frontend-viewport-test

@@ -45,7 +45,7 @@ main() {
     cd "$ROOT"
 
     # Test what ships: the production build, not a dev server.
-    "$ROOT/script/test"
+    "$ROOT/script/frontend-test"
     if [ ! -f "$ROOT/dist/index.html" ]; then
         echo "frontend-viewport-test: dist/index.html missing after build" >&2
         exit 1

script/lint

@@ -1,12 +1,21 @@
 #!/bin/sh
-# script/lint: run the linter (prettier in check mode).
+# script/lint: lint the whole repo: prettier over the frontend, then the
+# Go linter over backend/.
+#
+# The Go linter runs only in Docker: this builds the lint stage of
+# Dockerfile.backend, the digest-pinned golangci-lint image, which runs
+# the backend's fmt-check and lint targets. --no-cache makes the linter
+# really run every time rather than reuse an earlier result, and the
+# stage is built for its checks alone, so no image is kept.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    yarn prettier --check .
+    "$ROOT/script/frontend-lint"
+    timeout 300 docker build --no-cache --target lint \
+        --output type=cacheonly -f Dockerfile.backend .
 }
 
 main "$@"

script/test

@@ -1,13 +1,14 @@
 #!/bin/sh
-# script/test: run the test suite. This repo has no unit tests; the
-# production build serves as the test (fails on broken code).
+# script/test: run the test suite for the whole repo: the frontend at
+# the repo root, then the Go backend in backend/. Both halves together
+# get 30 seconds; each also keeps its own limit for the Dockerfiles.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    timeout 30 yarn build
+    timeout 30 sh -c 'script/frontend-test && backend/script/test'
 }
 
 main "$@"