TypeError: Cannot read properties of undefined (reading 'focus')

## Error

```
Cannot read properties of undefined (reading 'focus')
```

## Stack trace

```
../app/javascript/components/dropdowns/Reputation.tsx:95 in Reputation
div
Suspense
../node_modules/@sentry/react/src/errorboundary.tsx:101 in new ErrorBoundary
../node_modules/@tanstack/react-query/src/QueryClientProvider.tsx:30 in QueryClientProvider
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [TypeError: Cannot read properties of undefined (reading 'focus')](https://thalamus-ai.sentry.io/issues/144192628/)
- **Culprit**: d(app/javascript/components/dropdowns/useDropdown)
- **First seen:** Sep 1, 2026

Start at app/javascript/components/dropdowns/Reputation.tsx:95 and trace the focus call through app/javascript/components/dropdowns/useDropdown. Use the linked Sentry issue and stack trace to identify when the focus target is undefined. Done means the reported TypeError no longer occurs in the Reputation dropdown.

Written by the indexing model from the issue text.