Size icons and shapes with a prop instead of a Tailwind class

<x-icon size> writes --md-icon-size (24px by default) and takes the optical-size-20
cut for 20px or less, as M3 asks; mirror-rtl flips a directional symbol. <x-shape
size> writes --md-shape-size. Both draw from plain-CSS stylesheets in
material.components, gathered in components.css until all.css replaces it; a
caller's size class still wins while the other components are rewritten.
Plan steps 35 and 36, the prop every component rewrite depends on.

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

resources/css/components/shape.css

@@ -0,0 +1,13 @@
+/*
+ * <x-shape>: one of M3 Expressive's shapes, at `size` when one is given (`--md-shape-size`);
+ * otherwise the caller's own CSS sizes it.
+ */
+
+@layer material.reset, material.tokens, material.base, material.layout, material.components, material.text, material.visibility;
+
+@layer material.components {
+    [data-md-shape][style*='--md-shape-size'] {
+        inline-size: var(--md-shape-size);
+        block-size: var(--md-shape-size);
+    }
+}