feat: define simulator data contracts

packages/contracts/io.js

@@ -0,0 +1,22 @@
+export async function readJsonFile(file) {
+  try {
+    return JSON.parse(await file.text());
+  } catch (error) {
+    const reason = error instanceof Error ? error.message : String(error);
+    throw new Error(`${file.name} 파일은 올바른 JSON이 아닙니다: ${reason}`);
+  }
+}
+
+export function downloadJson(value, fileName) {
+  const body = `${JSON.stringify(value, null, 2)}\n`;
+  const url = URL.createObjectURL(new Blob([body], { type: "application/json" }));
+  const anchor = document.createElement("a");
+  anchor.href = url;
+  anchor.download = fileName;
+  anchor.click();
+  setTimeout(() => URL.revokeObjectURL(url), 0);
+}
+
+export function deepClone(value) {
+  return structuredClone(value);
+}