Function names remain mangled in Sentry stack traces after upgrading to Next.js 16 + Turbopack

### Is there an existing issue for this?

- [x] I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
- [x] I have reviewed the documentation https://docs.sentry.io/
- [x] I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

### How do you use Sentry?

Sentry Saas (sentry.io)

### Which SDK are you using?

@sentry/nextjs

### SDK Version

10.25.0

### Framework Version

Next 16.0.3

### Link to Sentry event

https://reevo-v7.sentry.io/issues/7041925983/events/1293cbdf13f54015b7cdde21ec9056de/

### Reproduction Example/SDK Setup

```
// instrumentation-client.ts
Sentry.init({
dsn: '',
environment: loggerEnv,
integrations: [
Sentry.replayIntegration({
maskAllText: false,
}),
Sentry.browserTracingIntegration(),
],
tracesSampleRate: 1,
replaysSessionSampleRate: 0,
replaysOnErrorSampleRate: 1.0,
enabled: true,
});

```

### Steps to Reproduce

1. Build and deploy — I’ve checked and the sourcemap is definitely being generated and shipped.
2. Trigger the error and take a look at the stack trace in the Sentry UI.

### Expected Result

With sourcemaps, the stack trace will show the real source code and the actual function name.

### Actual Result

The code shows up correctly as source, but the function name is still mangled—just like in the raw stack trace.

### Additional Context

_No response_

### Priority

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