adds design

docs/design/tokens/elevation.css

@@ -0,0 +1,8 @@
+/* Elevation is carried by the stone ramp, not by shadow. Shadows exist only for layers that
+   cross the page plane (dropdown, modal) and for the amber focus ring. */
+:root {
+  --shadow-none: none;
+  --shadow-dropdown: 0 4px 16px rgba(23, 28, 34, 0.10);
+  --shadow-modal: 0 16px 48px rgba(23, 28, 34, 0.18);
+  --ring-focus: 0 0 0 2px var(--color-amber-ring);
+}