ReferenceError: copy is not defined

## Error

```
copy is not defined
```

## Stack trace

```
:6
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [ReferenceError: copy is not defined](https://thalamus-ai.sentry.io/issues/146168520/)
- **Culprit**: ?()
- **First seen:** Sep 10, 2026

Start with the linked Sentry issue and its anonymous:6 stack entry, then search the website's JavaScript paths for the failing `copy` reference in the exercism-js flow. Trace the triggering action and reproduce the ReferenceError locally; done means the error no longer occurs and a regression test or documented reproduction verifies the fix.

Written by the indexing model from the issue text.