Add proper typing to integration test websocket mocks

Import and apply WsData type to the test server's websocket handlers
to ensure mock websocket objects match production typing.

src/integration.test.ts

@@ -1,7 +1,12 @@
 import { afterEach, beforeEach, describe, expect, test } from "bun:test";
 import type { ServerMessage } from "./protocol";
 import { decode } from "./protocol";
-import { getOrCreateSession, getSession, removeSession } from "./session";
+import {
+  type WsData,
+  getOrCreateSession,
+  getSession,
+  removeSession,
+} from "./session";
 
 describe("WebSocket concurrent edits integration", () => {
   let server: ReturnType<typeof Bun.serve>;
@@ -9,7 +14,7 @@ describe("WebSocket concurrent edits integration", () => {
 
   beforeEach(() => {
     // start server for each test
-    server = Bun.serve({
+    server = Bun.serve<WsData>({
       port: PORT,
       fetch(req, server) {
         const url = new URL(req.url);