initial: webhook telegram adapter for pi with streaming replies

- webhook server with secret validation, rate limiting, body guards
- streaming replies via sendMessage + editMessageText throttled loop
- RPC session management for persistent conversations
- 15/15 tests passing

vitest.config.ts

@@ -0,0 +1,8 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: "node",
+  },
+});