Use empty string for NONE margin values

[pglevy]

Problem

Margin mappings inconsistently handle the NONE value - some use explicit mt-0/mb-0 classes, while newer components (TabsField) use empty string.

Current Patterns

Older Pattern

const marginAboveMap = {
  NONE: 'mt-0',  // Explicit zero class
  EVEN_LESS: 'mt-1',
  // ...
}

Newer Pattern (TabsField)

const marginMap = {
  NONE: '',  // Empty string, cleaner
  EVEN_LESS: 'mt-1',
  // ...
}

Recommendation

Use empty string '' for NONE values across all components. Benefits:

• Cleaner output HTML (no unnecessary mt-0 classes)
• Follows Tailwind best practices (no class = default browser behavior)
• Consistent with newer component patterns

Affected Components

• ButtonArrayLayout
• CardLayout
• TagField

Priority

Low - cosmetic improvement, but increases consistency

Note

If implementing the shared margin utility (#1), this should be incorporated into that solution.