Add Tree of Art start page with fixed lineage geometry and shareable layout links.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/pages/HomePage.css

@@ -44,6 +44,9 @@
   top: 16px;
   left: 16px;
   z-index: 120;
+  display: flex;
+  gap: 8px;
+  align-items: center;
 }
 
 .site-layout-link {
@@ -63,6 +66,17 @@
   color: #f5e6c8;
 }
 
+/* Link to the alternative tree start page — the one worth noticing. */
+.site-layout-link-feature {
+  border-color: rgba(201, 169, 110, 0.7);
+  background: rgba(201, 169, 110, 0.16);
+  color: #f5e6c8;
+}
+
+.site-layout-link-feature:hover {
+  background: rgba(201, 169, 110, 0.3);
+}
+
 .gallery-session-suspended {
   position: fixed;
   inset: 0;