Replace the boxed-text-field form with the family's tonal-card layout:
Close + filled SAVE top bar, a borderless headline title with a
list-colour accent bar, a "When" card (all-day switch + tappable
start/due rows), a tappable list card and reminder card that open
OptionCard dialogs, and segmented-button priority.
Optional Description / Priority / Reminder sections unfold from a
"More fields" picker (Calendula's disclosure): TaskFormField enum +
populatedFields() auto-reveal fields that already carry a value, and a
persisted defaultEditFields pref decides which start open (the settings
UI to edit it lands with M6). New shared InlineTextField + OptionCard;
date/time conversion helpers in DateTimeField promoted to internal.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>