feat: define closed portfolio input contract

src/content/asset-url.ts

@@ -0,0 +1,12 @@
+import type { PublicAssetManifest } from './types.ts';
+
+export const assetUrl = (manifest: PublicAssetManifest, assetId: string, base = '/assets/'): string => {
+  if (!base.startsWith('/') || base.startsWith('//') || /[?#]/u.test(base)) {
+    throw new Error('Asset URL base must be an absolute path without a query or fragment.');
+  }
+  const asset = manifest.assets.find((candidate) => candidate.id === assetId);
+  if (asset === undefined) {
+    throw new Error(`Unknown asset ID: ${assetId}`);
+  }
+  return `${base.endsWith('/') ? base : `${base}/`}${encodeURIComponent(asset.fileName)}`;
+};