fix(telegram): restrict native fetch to bun

src/telegram/fetch.ts

@@ -1,15 +1,13 @@
-// Ensure native fetch is used when available (Bun + Node 18+).
+// Bun-only: force native fetch to avoid grammY's Node shim under Bun.
 export function resolveTelegramFetch(
   proxyFetch?: typeof fetch,
 ): typeof fetch | undefined {
   if (proxyFetch) return proxyFetch;
   const fetchImpl = globalThis.fetch;
   const isBun = "Bun" in globalThis || Boolean(process?.versions?.bun);
+  if (!isBun) return undefined;
   if (!fetchImpl) {
-    if (isBun) {
-      throw new Error("fetch is not available; set telegram.proxy in config");
-    }
-    return undefined;
+    throw new Error("fetch is not available; set telegram.proxy in config");
   }
   return fetchImpl;
 }