NumberField and CssField steppers gain a `stacked` compact layout and
themeable default glyphs.
- Glyphs render from recipe tokens via `:empty::before` (split plus/minus,
stacked up/down triangles); passing children overrides per instance,
a theme overrides the token. 4 tokens per component, unicode-escaped.
- CssField gains the `steppers` prop (split | stacked); its stacked layout
mirrors NumberField (self-contained — the split layout left untouched).
- NumberField split: square buttons flush to the field edge with an inner
divider and higher hover/focus contrast (control-radius 0).
- Stacked rows use minmax(0,1fr) + a height-proportional glyph so the two
arrows stay symmetric and uncut at xs.
- Demos: steppers controls + stepper-layout / sizes / themed-glyph
showcases; code snippets use the themed defaults.
- Docs: THEMING section 33, number-field and css-field READMEs.
Note: also sweeps in the pre-existing palabras WIP already in the tree.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>