Telegram: use Grammy types directly, add typed Probe/Audit to plugin interface (#8403)

* Telegram: replace duplicated types with Grammy imports, add Probe/Audit generics to plugin interface

* Telegram: remove legacy forward metadata (deprecated in Bot API 7.0), simplify required-field checks

* Telegram: clean up remaining legacy references and unnecessary casts

* Telegram: keep RequestInit parameter type in proxy fetch (addresses review feedback)

* Telegram: add exhaustiveness guard to resolveForwardOrigin switch

src/telegram/proxy.ts

@@ -1,11 +1,14 @@
-// @ts-nocheck
 import { ProxyAgent, fetch as undiciFetch } from "undici";
 import { wrapFetchWithAbortSignal } from "../infra/fetch.js";
 
 export function makeProxyFetch(proxyUrl: string): typeof fetch {
   const agent = new ProxyAgent(proxyUrl);
-  return wrapFetchWithAbortSignal((input: RequestInfo | URL, init?: RequestInit) => {
-    const base = init ? { ...init } : {};
-    return undiciFetch(input, { ...base, dispatcher: agent });
-  });
+  // undici's fetch is runtime-compatible with global fetch but the types diverge
+  // on stream/body internals. Single cast at the boundary keeps the rest type-safe.
+  const fetcher = (input: RequestInfo | URL, init?: RequestInit) =>
+    undiciFetch(input as string | URL, {
+      ...(init as Record<string, unknown>),
+      dispatcher: agent,
+    }) as unknown as Promise<Response>;
+  return wrapFetchWithAbortSignal(fetcher);
 }