`AtomLayout::gap` is an `Option`, where `None` means "use the theme value".
`AtomLayoutStyle::apply` set it unconditionally, so it clobbered the gap a
widget had asked for. `DragValue` sets `gap(0.0)` to keep its prefix, value and
suffix flush, and lost it, which widened every `DragValue` in the demos.
`apply` now fills the gap in only when the widget left it unset. This also
reverts the snapshot updates that had captured the wider gap.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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