feat(art): add living hedge SVG review library

docs/UI_STYLE.md

@@ -134,6 +134,30 @@ are not MVP requirements.
   `rate_limited` still darkens and blurs only the maze for at most 520 ms.
 - Reduced-motion mode uses static deformation and the same trampled-gap state.
 
+### Hedge art review contract
+
+- Hedge samples are direct top-down vectors for review only; they are not
+  runtime assets in this milestone. A segment occupies one cell edge and uses
+  a centered, 10 CSS-pixel-wide foliage band at 40 CSS pixels per cell, scaling
+  proportionally at 34 and 46 pixels.
+- The family uses deep shadow `#173d2a`, branch `#765033`, foliage dark
+  `#296443`, foliage mid `#4f9b55`, foliage light `#8cc968`, and pale leaf
+  highlight `#c7e68a`. A dark outline and branch fork preserve silhouette in
+  grayscale; color is supplementary depth, not the only boundary cue.
+- Each intact symbol combines three or more named leaf clusters with visible
+  twig forks, a restrained shadow, and an irregular outer silhouette. Straight
+  symbols tile end-to-end without double borders; corner, crossing, and end
+  symbols share their edge centre and may rotate or mirror without directional
+  lighting.
+- Impact stages one through four retain the same wall centre while increasingly
+  compressing foliage, bending twigs, and shedding a fixed small number of
+  leaves. The breakthrough and trampled symbols leave a clear centred passage
+  at least 16 CSS pixels wide at 40-pixel scale, with flattened vegetation on
+  both sides. They never imply movement beyond that one authoritative edge.
+- Review sheets show the source symbols on neutral and dark-cell backgrounds
+  at 34, 40, and 46 CSS pixels. They contain no coordinates, objects,
+  ownership, hidden topology, animation, or runtime dependencies.
+
 ## 8. Responsive behavior
 
 - The minimum supported player viewport is `412 x 916` CSS pixels.