- MuiOutlinedInput: error border and focus ring now use copper
(ColorTextBrand #B0610F) instead of red (ColorFeedbackError #BC2F2F)
- MuiFormHelperText: error text colour overridden to copper
- MuiFormLabel: error state stays neutral text (D024 reinforcement)
- ToggleButtonGroup: error border changed from error.main to copper
palette.error.main remains red for non-form uses (destructive buttons,
system alerts). Form validation is now fully warm/copper end-to-end.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>