[Bug]: TypeError: Cannot read properties of null (reading 'accept') during connectDevtools()

### Version

1.3.0

### Steps to reproduce

```ts
import { Stagehand } from "@browserbasehq/stagehand";
import { endpointURLString } from "@cloudflare/playwright";
import { z } from "zod";

export default {
async fetch(request, env) {
const stagehand = new Stagehand({
env: "LOCAL",
localBrowserLaunchOptions: { cdpUrl: endpointURLString(env.BROWSER) },
modelName: "google/gemini-3-flash-preview",
modelClientOptions: { apiKey: env.GOOGLE_API_KEY },
verbose: 1,
});

await stagehand.init(); // throws here in production
...
},
} satisfies ExportedHandler;
```

put above code into worker

### Expected behavior

`stagehand.init()` resolves and `stagehand.page` is usable, same as under `wrangler dev`.

### Actual behavior

```json
{
"category": "init",
"message": "connecting to local browser via CDP URL",
"level": 1,
"auxiliary": {
"cdpUrl": {
"value": "http://fake.host/v1/devtools/browser?browser_binding=BROWSER",
"type": "string"
}
}
}
{
"message": "Error in init:",
"level": 0,
"auxiliary": {
"error": {
"value": "TypeError: Cannot read properties of null (reading 'accept')",
"type": "string"
}
}
}
{
"message": "The browser context is undefined. This means the CDP connection to the browser failed. If running locally, please check if the browser is running and the port is open.",
"level": 0
}
```

### Additional context

local isn't affected, but prod environment can't use stagehand

### Environment

```shell
- `wrangler`: 4.107.0
- `@cloudflare/playwright`: 1.3.0
- `@browserbasehq/stagehand`: 2.5.9
- `wrangler.jsonc`:

{
"compatibility_date": "2026-07-09",
"compatibility_flags": ["nodejs_compat"],
"browser": { "binding": "BROWSER" },
"alias": { "playwright": "@cloudflare/playwright" }
}

- Workers plan: Paid (Browser Rendering requires it)
```

Start with the `Stagehand.init()` call and the `connectDevtools()` path named in the issue, then compare the production Worker CDP connection with the working `wrangler dev` case. Use the provided Worker setup and versions to investigate; done means `stagehand.init()` resolves in production and `stagehand.page` is usable.

Written by the indexing model from the issue text.