feat: auto-install missing build dependencies (pnpm, bun, nfpm)

Build scripts now check for required tools before building and install
them automatically if missing. Handles both amd64 and arm64 host systems.

- pnpm: installed via corepack or npm
- bun: installed via official install script
- nfpm: downloaded from GitHub for the correct host architecture
- node_modules: runs pnpm install if missing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/ensure-deps.sh

@@ -0,0 +1,120 @@
+#!/bin/bash
+# Ensure build dependencies are installed.
+# Source this file from build scripts: source "$SCRIPT_DIR/ensure-deps.sh"
+#
+# Checks for: node, pnpm, bun, nfpm
+# Auto-installs missing tools. Uses npm for pnpm/bun, downloads nfpm binary.
+
+NFPM_VERSION="${NFPM_VERSION:-2.45.0}"
+
+_ensure_node() {
+  if command -v node &>/dev/null; then
+    return
+  fi
+
+  echo "ERROR: Node.js is required but not installed."
+  if command -v dnf &>/dev/null; then
+    echo "  Install with: sudo dnf install nodejs"
+  elif command -v apt &>/dev/null; then
+    echo "  Install with: sudo apt install nodejs npm"
+  else
+    echo "  Install from: https://nodejs.org/"
+  fi
+  exit 1
+}
+
+_ensure_pnpm() {
+  if command -v pnpm &>/dev/null; then
+    return
+  fi
+
+  echo "==> pnpm not found, installing..."
+  if command -v corepack &>/dev/null; then
+    corepack enable
+    corepack prepare pnpm@9.15.0 --activate
+  else
+    npm install -g pnpm
+  fi
+
+  # Verify
+  if ! command -v pnpm &>/dev/null; then
+    echo "ERROR: pnpm installation failed."
+    echo "  Try manually: npm install -g pnpm"
+    exit 1
+  fi
+  echo "    Installed pnpm $(pnpm --version)"
+}
+
+_ensure_bun() {
+  if command -v bun &>/dev/null; then
+    return
+  fi
+
+  echo "==> bun not found, installing..."
+  # bun's official install script handles both amd64 and arm64
+  curl -fsSL https://bun.sh/install | bash
+
+  # Add to PATH for this session
+  export PATH="$HOME/.bun/bin:$PATH"
+
+  if ! command -v bun &>/dev/null; then
+    echo "ERROR: bun installation failed."
+    echo "  Try manually: curl -fsSL https://bun.sh/install | bash"
+    exit 1
+  fi
+  echo "    Installed bun $(bun --version)"
+}
+
+_ensure_nfpm() {
+  if command -v nfpm &>/dev/null; then
+    return
+  fi
+
+  echo "==> nfpm not found, installing v${NFPM_VERSION}..."
+
+  # Detect host arch for the nfpm binary itself (not the target arch)
+  local dl_arch
+  case "$(uname -m)" in
+    x86_64)  dl_arch="x86_64" ;;
+    aarch64) dl_arch="arm64" ;;
+    arm64)   dl_arch="arm64" ;;
+    *)       dl_arch="x86_64" ;;
+  esac
+
+  local url="https://github.com/goreleaser/nfpm/releases/download/v${NFPM_VERSION}/nfpm_${NFPM_VERSION}_Linux_${dl_arch}.tar.gz"
+  local install_dir="$HOME/.local/bin"
+  mkdir -p "$install_dir"
+
+  curl -sL -o /tmp/nfpm.tar.gz "$url"
+  tar xzf /tmp/nfpm.tar.gz -C "$install_dir" nfpm
+  rm -f /tmp/nfpm.tar.gz
+
+  export PATH="$install_dir:$PATH"
+
+  if ! command -v nfpm &>/dev/null; then
+    echo "ERROR: nfpm installation failed."
+    echo "  Download manually from: https://github.com/goreleaser/nfpm/releases"
+    exit 1
+  fi
+  echo "    Installed nfpm $(nfpm --version) to $install_dir"
+}
+
+_ensure_npm_deps() {
+  if [ -d node_modules ]; then
+    return
+  fi
+
+  echo "==> node_modules not found, running pnpm install..."
+  pnpm install --frozen-lockfile
+}
+
+ensure_build_deps() {
+  echo "==> Checking build dependencies..."
+  _ensure_node
+  _ensure_pnpm
+  _ensure_bun
+  _ensure_nfpm
+  _ensure_npm_deps
+  echo "    All build dependencies OK"
+  echo ""
+}