Fixes production error "Cannot read properties of undefined (reading 'carryBoxes')"
that occurred when users tried to adjust difficulty settings.
Root cause: displayRules was undefined for new users or users with old V1 config
in database. Difficulty adjustment buttons accessed displayRules.carryBoxes without
checking if displayRules existed first.
Changes:
- AdditionWorksheetClient: Initialize displayRules with defaults when missing
- ConfigPanel: Use null-coalescing operators instead of non-null assertions
- ConfigPanel: Add error logging when required fields are missing
- NEW: WorksheetErrorBoundary component to catch all errors in worksheet page
- page.tsx: Wrap client component with error boundary
This ensures users see helpful error messages instead of blank pages,
and never need to open the browser console to understand what went wrong.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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