[Bug] WebSocket messages received as "[object Blob]" in dev mode

[ValentinKolb]

Bug Description

As discussed in #163, when sending WebSocket messages in dev mode, the server receives the literal string "[object Blob]" instead of the actual message content.

Steps to Reproduce

// Client code
const socket = new WebSocket('ws://localhost:4321/api/ws');
socket.onopen = () => {
  socket.send("foo");
};

// Server receives: "[object Blob]"
// Expected: "foo"

Environment

• Using bunx to run dev server
• astro-bun-websocket with gratelets/bun-websocket package

Root Cause

The issue appears to be related to how the dev middleware handles message conversion when the underlying ws package receives data. The data is incorrectly converted to string, resulting in the default JavaScript object toString representation.