Complete training workflow and acceptance hardening

frontend/scripts/precompress-assets.mjs

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+import { readdir, readFile, stat, utimes, writeFile } from "node:fs/promises";
+import { gzip } from "node:zlib";
+import { promisify } from "node:util";
+
+const gzipAsync = promisify(gzip);
+const assetDirectory = new URL("../dist/assets/", import.meta.url);
+const compressedExtensions = /\.(?:js|css|json|svg)$/i;
+const minimumBytes = 1024;
+let compressedCount = 0;
+let sourceBytes = 0;
+let gzipBytes = 0;
+
+async function compressAssets(directory) {
+  for (const entry of await readdir(directory, { withFileTypes: true })) {
+    const path = new URL(`${entry.name}${entry.isDirectory() ? "/" : ""}`, directory);
+    if (entry.isDirectory()) {
+      await compressAssets(path);
+      continue;
+    }
+    if (!compressedExtensions.test(entry.name)) continue;
+
+    const info = await stat(path);
+    if (info.size < minimumBytes) continue;
+    const source = await readFile(path);
+    const compressed = await gzipAsync(source, { level: 9 });
+    const compressedPath = new URL(`${entry.name}.gz`, directory);
+    await writeFile(compressedPath, compressed);
+    // Nginx gzip_static can safely pair the sidecar with its source file.
+    await utimes(compressedPath, info.atime, info.mtime);
+    compressedCount += 1;
+    sourceBytes += source.byteLength;
+    gzipBytes += compressed.byteLength;
+  }
+}
+
+await compressAssets(assetDirectory);
+console.log(
+  `Precompressed ${compressedCount} assets: ${sourceBytes} -> ${gzipBytes} bytes`,
+);