Render DateTimeField from Form with variant: 'datetime'

[david-roper]

Render DateTimeField from Form with variant: 'datetime'

The DateTimeField component already exists, but Form had no way to render it. This PR lets a date field opt into date + time input by setting variant: 'datetime'. Either way, the form stores a single Date.

const content = {
  appointment: {
    kind: 'date',
    label: 'Appointment',
    variant: 'datetime'
  }
};

Changes

• Dependency: upgrades @douglasneuroinformatics/libui-form-types from ^1.4.0 to ^1.5.0. That version adds the optional variant?: 'date' | 'datetime' to date fields, defaulting to 'date'.
• ScalarField: for kind: 'date', renders DateTimeField when variant === 'datetime' and DateField otherwise, so existing date fields are unaffected.
• DateTimeField: props now come from DateFormField (minus kind and variant) instead of BaseFormField, so they match the form field type.
• Stories: the Form story gains a dateTime field ("Date and Time"), and WithInitialValues sets it.
• Tests: Form.test.tsx gains two tests:
  • variant: 'datetime' renders the date button and time input, not the date-only input.
  • With no variant, only the date-only input renders.

Notes for reviewers

• timeFormat="24h" (the segmented 24-hour time input) isn't in the form field type, so fields rendered through Form always use the native time input, which follows the browser locale. Supporting 24h there would need a matching option in libui-form-types.

Testing

• tsc passes
• vitest run: 217/217 tests pass

🤖 Generated with Claude Code

Closes issue #122

[github-actions]

🎉 This PR is included in version 6.18.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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