fix: use POSIX sh instead of bash for Alpine CI compatibility

The node:22-alpine container doesn't have bash installed,
causing `sh: bash: not found` in the build step.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

package.json

@@ -7,7 +7,7 @@
     "dev": "slidev decks/demo/slides.md",
     "dev:demo": "slidev decks/demo/slides.md",
     "dev:showcase": "slidev decks/showcase/slides.md",
-    "build": "bash scripts/build.sh",
+    "build": "sh scripts/build.sh",
     "build:demo": "slidev build decks/demo/slides.md --base /demo/ --out dist/demo",
     "build:showcase": "slidev build decks/showcase/slides.md --base /showcase/ --out dist/showcase",
     "serve": "pnpm run build && pnpm exec serve dist -l 3030",

scripts/build.sh

@@ -1,5 +1,5 @@
-#!/usr/bin/env bash
-set -euo pipefail
+#!/bin/sh
+set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd)"
 DIST="$ROOT/dist"