Deno + WebAssembly - fails at toBuffer() "em-pthread" maximum call stack exceeded

Nobody has claimed this yet.

Here's a simple repro where importing sharp does not cause an issue with deno. But actually using it to encode an image fails due to toBuffer(). The prior issue about refHandle.ref etc, was fixed at https://github.com/toyobayashi/emnapi/pull/142.

https://github.com/gvkhna/deno-sharp-wasm-test

That produces the following:

```
error: Uncaught (in worker "em-pthread") RangeError: Maximum call stack size exceeded
at postMessage (file:///Users/.../github/deno-sharp-wasm-test/node_modules/@img/sharp-wasm32/lib/sharp-wasm32.node.js:1:1)
at postMessage (file:///Users/.../github/deno-sharp-wasm-test/node_modules/@img/sharp-wasm32/lib/sharp-wasm32.node.js:1:1)
at postMessage (file:///Users/.../github/deno-sharp-wasm-test/node_modules/@img/sharp-wasm32/lib/sharp-wasm32.node.js:1:1)
at postMessage (file:///Users/.../github/deno-sharp-wasm-test/node_modules/@img/sharp-wasm32/lib/sharp-wasm32.node.js:1:1)
at postMessage (file:///Users/.../github/deno-sharp-wasm-test/node_modules/@img/sharp-wasm32/lib/sharp-wasm32.node.js:1:1)
```

After some simple logging and isolation. I've isolated the issue to be here:

In sharp-wasm32.node.js:
```javascript
if (ENVIRONMENT_IS_PTHREAD) {
var wasmModuleReceived;
if (ENVIRONMENT_IS_NODE) {
var parentPort = worker_threads["parentPort"];
parentPort.on("message", msg => {
onmessage({
data: msg
}) });

Object.assign(globalThis, {
self: global,
postMessage: msg => {
// postMessage is calling itself here...
parentPort.postMessage(msg)
}
})
}
```

On Deno 2.2.6
Latest version of sharp/sharp-wasm.

Run the linked deno-sharp-wasm-test reproduction with Deno 2.2.6 and inspect sharp-wasm32.node.js around the ENVIRONMENT_IS_PTHREAD postMessage setup. Trace why postMessage recurses through the worker path, then verify that image encoding via toBuffer() completes without a maximum call stack error.

Written by the indexing model from the issue text.