Split viewer and simulation into separate apps

apps/viewer/src/api.ts

@@ -0,0 +1,19 @@
+import type { WorldSnapshot } from "./contracts";
+
+export async function fetchWorldSnapshot(signal?: AbortSignal) {
+  const response = await fetch("/api/world", { signal });
+  if (!response.ok) {
+    throw new Error(`World request failed with ${response.status}`);
+  }
+  return response.json() as Promise<WorldSnapshot>;
+}
+
+export async function resetWorld() {
+  const response = await fetch("/api/world/reset", {
+    method: "POST",
+  });
+  if (!response.ok) {
+    throw new Error(`Reset request failed with ${response.status}`);
+  }
+  return response.json() as Promise<WorldSnapshot>;
+}