The first commit, the core and all files is adding to repo

scripts/assets.mjs

@@ -0,0 +1,48 @@
+import { mkdir, readFile, writeFile, access } from "node:fs/promises";
+import { createHash } from "node:crypto";
+import { unzipSync } from "fflate";
+export const assetsRoot = ".cache/minecraft/1.21.11";
+export async function prepareAssets() {
+  try {
+    await access(`${assetsRoot}/assets/minecraft/blockstates/grass_block.json`);
+    return;
+  } catch {}
+  const manifest = await (
+    await fetch(
+      "https://piston-meta.mojang.com/mc/game/version_manifest_v2.json",
+    )
+  ).json();
+  const entry = manifest.versions.find((v) => v.id === "1.21.11");
+  if (!entry) throw new Error("Official Minecraft 1.21.11 metadata missing");
+  const version = await (await fetch(entry.url)).json();
+  await mkdir(".cache/minecraft", { recursive: true });
+  const jarPath = ".cache/minecraft/client-1.21.11.jar";
+  let jar;
+  try {
+    jar = await readFile(jarPath);
+  } catch {
+    const response = await fetch(version.downloads.client.url);
+    if (!response.ok) throw new Error("Minecraft asset download failed");
+    jar = Buffer.from(await response.arrayBuffer());
+    await writeFile(jarPath, jar);
+  }
+  if (
+    createHash("sha1").update(jar).digest("hex") !==
+    version.downloads.client.sha1
+  )
+    throw new Error("Minecraft client checksum mismatch");
+  const entries = unzipSync(jar, {
+    filter: (f) =>
+      /^assets\/minecraft\/(models|blockstates|textures\/block)\//.test(
+        f.name,
+      ) && /\.(json|png)$/.test(f.name),
+  });
+  for (const [name, bytes] of Object.entries(entries)) {
+    const path = `${assetsRoot}/${name}`;
+    await mkdir(path.slice(0, path.lastIndexOf("/")), { recursive: true });
+    await writeFile(path, bytes);
+  }
+  console.log(
+    `Prepared ${Object.keys(entries).length} verified vanilla model/texture assets.`,
+  );
+}