🐛 Bug Report — Runtime APIs -- PromiseFulfiller destroyed without fulfilling promise in Vitest tests on Windows 11

## What is the problem?

When running Vitest tests on **Windows 11**, tests that make HTTP requests to the worker fail with a `PromiseFulfiller was destroyed without fulfilling the promise` error. The same tests work perfectly on **macOS**.

**Working scenarios:**
- Worker runs correctly with `npx wrangler dev` on both platforms
- Worker deployment and runtime work correctly on both platforms
- Vitest tests work correctly on macOS

**Failing scenario:**
- Vitest tests fail on Windows 11 with the error below

## What are the error messages?

```
workerd/jsg/util.c++:320: error: e = kj/async.c++:3136: failed: PromiseFulfiller was destroyed without fulfilling the promise.
stack: 7ff7969fd065 7ff79659eedd 7ff796c9557f 7ff7969fd866 7ff7969f7d62 7ff79659fd8b 7ff7969f833b 7ff796a24573 7ff7969f7e3c 7ff7969feb3f 7ff796a00c51 7ff7969f6397 7ff79539396b 7ff796a4a4ff 7ff796a516a6 7ff796a4aa03 7ff79538b500 0 0 0 0 0; sentryErrorContext = jsgInternalError; wdErrId = 6gissi69k74mnt6i9b5um3ud
```

## What is the expected behavior?

Tests should run successfully on both macOS and Windows 11, similar to how the worker works correctly with `npx wrangler dev` on both platforms.

## What is the actual behavior?

Tests fail on Windows 11 with the promise lifecycle error, while working correctly on macOS.

## Code sample

### vitest.config.ts
```typescript
import { defineWorkersConfig } from "@cloudflare/vitest-pool-workers/config";

export default defineWorkersConfig({
test: {
poolOptions: {
workers: {
isolatedStorage: false,
wrangler: { configPath: "./wrangler.jsonc" },
miniflare: {
"env": {
"dev" : {
"workflows": [
{
"name": "workflows",
"binding": "MY_WORKFLOW",
"class_name": "MyWorkflow"
}
]
}
},
}
},
},
},
});
```

### wrangler.jsonc
```json
{
"name": "test-worker",
"main": "src/routes/api.ts",
"compatibility_date": "2025-03-17",
"compatibility_flags": [
"nodejs_compat",
"nodejs_compat_populate_process_env"
],
"vars": {
"ENVIRONMENT": "local"
},
"env": {
"dev" : {
"vars": {
"ENVIRONMENT": "dev"
},
"workflows": [
{
"name": "workflows",
"binding": "MY_WORKFLOW",
"class_name": "MyWorkflow"
}
]
},
"prod" : {
"vars": {
"ENVIRONMENT": "prod",
},
"workflows": [
{
"name": "workflows",
"binding": "MY_WORKFLOW",
"class_name": "MyWorkflow"
}
]
}
},
"assets": {
"directory": "public"
},
"durable_objects": {
"bindings": [
{
"name": "WorkerAgent",
"class_name": "WorkerAgent"
},
{
"name": "Manager",
"class_name": "Manager"
},
{
"name": "ChatAgent",
"class_name": "ChatAgent"
}
]
},
"migrations": [
{
"tag": "v1",
"new_sqlite_classes": [
"WorkerAgent", "Manager", "ChatAgent",
]
}
],
"workflows": [
{
"name": "workflows",
"binding": "MY_WORKFLOW",
"class_name": "MyWorkflow"
}
],
"observability": {
"enabled": true
}
}
```

### Test that fails
```typescript
it("should handle API request successfully", async () => {
const payload = {
amount: 100,
reason: "Test data"
};

const request = new Request("http://127.0.0.1:8787/api/endpoint", {
method: "POST",
headers: {
"Content-Type": "application/json",
"Authorization": "Basic [redacted]"
},
body: JSON.stringify(payload),
});

const ctx = createExecutionContext();

try {
const response = await app.fetch(request, env, ctx);
await waitOnExecutionContext(ctx);

expect(response.status).toBe(200);
// Additional assertions...
} catch (error) {
console.error("Test error:", error);
throw error;
}
});
```

## What version of workerd are you using?

From package.json:
- `@cloudflare/vitest-pool-workers`: ^0.8.5
- `vitest`: ^3.0.9
- `wrangler`: ^4.23.0
- `@cloudflare/vite-plugin`: 0.1.16
- `vite`: ^6.2.3

## What operating system are you using?

- **macOS**: Tests work correctly
- **Windows 11**: Tests fail

## Additional context

- The issue appears to be platform-specific (Windows 11 vs macOS)
- The error suggests a promise lifecycle issue within the workerd runtime
- All external API calls work correctly outside of the Vitest environment

This appears to be a platform-specific issue in workerd's promise handling, potentially related to how the Windows version manages promise lifecycles during test execution compared to the macOS version.