Take colour off the overshooting spatial spring

Four components animated background-color and color on ease-spatial-fast, whose
fast variant peaks at 1.094 — the one thing tokens/motion.css says a colour must
never do. Tailwind cannot emit two springs on one element, so a small unlayered
file gives shape and size the spatial spring and colour and elevation the
effects one in a single property list. Plan step 18, actions.md ACT-19.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

resources/views/components/button.blade.php

@@ -9,7 +9,9 @@
      `size` is Expressive's scale — `xs` 32px, `sm` 40px (the default), `md` 56px, `lg` 96px,
      `xl` 136px — each with its own padding, type style and icon size. `shape` is `round` (the
      default) or `square`; either one squares off towards a smaller corner while pressed, on the
-     fast spatial spring.
+     fast spatial spring, while the colours cross on the fast effects spring beside it
+     (`state-transition-fast`, resources/css/components/actions.css: a colour must never
+     overshoot).
 
      With an `icon` and no label it is an icon button: `width` is `narrow`, `default` or `wide`,
      `variant="text"` is M3's standard icon button, and the tooltip or label names it for screen
@@ -164,7 +166,7 @@
 
     $classes = [
         'group/button state-layer focus-ring inline-flex shrink-0 cursor-pointer select-none items-center justify-center whitespace-nowrap',
-        'transition-[border-radius,background-color,color,box-shadow,padding,margin] duration-(--md-sys-motion-spatial-fast-duration) ease-spatial-fast',
+        'state-transition-fast',
         $dimensions,
         // A composite component (a split button's halves) passes the corners its place needs.
         $corners ?? $corner.' '.$pressed[$size],