SyntaxError: Unexpected token '<'

## Error

```
Unexpected token '<'
```

## Stack trace

```
/users/sign_in:1
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [SyntaxError: Unexpected token '<'](https://thalamus-ai.sentry.io/issues/131523491/)
- **Culprit**: ?(users/sign_in)
- **First seen:** Jul 1, 2026

Start by reviewing the Sentry report for issue 131523491 and reproducing the /users/sign_in request in the website. Trace why that route produces the Unexpected token '<' error, then verify that the sign-in page loads without the reported SyntaxError.

Written by the indexing model from the issue text.