feat(extension): redesign welcome page with Prism.js syntax highlighting

extension/scripts/download-prism.ts

@@ -0,0 +1,42 @@
+// Downloads Prism.js assets into dist/src/ for the welcome page.
+// Chrome extension CSP blocks external scripts, so we bundle them locally.
+import https from 'node:https'
+import fs from 'node:fs'
+import path from 'node:path'
+
+const BASE = 'https://cdnjs.cloudflare.com/ajax/libs/prism/1.29.0/'
+const DEST = path.join('dist', 'src')
+
+const files: [string, string][] = [
+  ['prism.min.js', 'prism.min.js'],
+  ['components/prism-bash.min.js', 'prism-bash.min.js'],
+]
+
+function download(url: string, dest: string): Promise<void> {
+  return new Promise((resolve, reject) => {
+    https.get(url, (res) => {
+      if (res.statusCode !== 200) {
+        reject(new Error(`Failed to download ${url}: ${res.statusCode}`))
+        return
+      }
+      const chunks: Buffer[] = []
+      res.on('data', (chunk: Buffer) => { chunks.push(chunk) })
+      res.on('end', () => {
+        fs.writeFileSync(dest, Buffer.concat(chunks))
+        resolve()
+      })
+      res.on('error', reject)
+    }).on('error', reject)
+  })
+}
+
+async function main() {
+  await Promise.all(
+    files.map(([src, dest]) => {
+      return download(BASE + src, path.join(DEST, dest))
+    })
+  )
+  console.log(`Downloaded ${files.length} Prism.js files to ${DEST}`)
+}
+
+main()