feat(htmx-css): ToggleGroup support + padding/primary parity

Generator (scripts/generate-htmx-css.ts): track `viaVariants` per slot so
slots that compose another component's variant system (e.g. ToggleGroupItem
via toggleVariants) inherit the referenced CVA's base + variant rules under
their own selector. Previously toggle-group-item's CSS contained only its
override classes, shipping with no padding/height/hover/active state.

Toggle (components/ui/toggle.tsx):
  - data-[state=on] now uses bg-primary (orange) instead of bg-accent (grey),
    matching every other "commit" affordance in the palette.
  - Horizontal padding aligned with Button: px-4/px-3/px-6 per size, plus
    has-[>svg]:px-* for icon-only toggles.

ToggleGroup (components/ui/toggle-group.tsx): drop min-w-0 flex-1 shrink-0
from the item override. Items now size to content instead of being clamped
into equal narrow columns where longer labels overflowed the bg box.

Showcase: add ToggleGroup section to the React page (component-matrix.tsx)
and 1:1 HTMX mirror (public/htmx.html) with a new JS bridge branch for
single/multi-select. compare-all.sh extended with the new section; 22/22
pass at ≥99.97%.

Docs: GAPS.md captures the generator gap, overflow root cause, color
rationale, and padding parity with before/after numbers.

components/ui/toggle-group.tsx

@@ -60,7 +60,7 @@ function ToggleGroupItem({
           variant: context.variant || variant,
           size: context.size || size,
         }),
-        'min-w-0 flex-1 shrink-0 rounded-none shadow-none first:rounded-l-md last:rounded-r-md focus:z-10 focus-visible:z-10 data-[variant=outline]:border-l-0 data-[variant=outline]:first:border-l',
+        'rounded-none shadow-none first:rounded-l-md last:rounded-r-md focus:z-10 focus-visible:z-10 data-[variant=outline]:border-l-0 data-[variant=outline]:first:border-l',
         className,
       )}
       {...props}