iter(g48): 新增 splitter 可拖拽分栏容器

packages/skin/ui/ui.css

@@ -2671,3 +2671,53 @@ button.ua-step-dot:hover {
   .ua-cascader-caret,
   .ua-cascader-opt { transition: none; }
 }
+.ua-splitter {
+  display: flex;
+  width: 100%;
+  min-height: 160px;
+  border: 1px solid var(--ua-color-border);
+  border-radius: var(--ua-radius-md);
+  background: var(--ua-color-surface);
+  overflow: hidden;
+}
+.ua-splitter-vertical {
+  flex-direction: column;
+}
+.ua-splitter-pane {
+  flex: 0 0 auto;
+  min-width: 0;
+  min-height: 0;
+  padding: var(--ua-space-2);
+  overflow: auto;
+}
+.ua-splitter-bar {
+  position: relative;
+  flex: 0 0 6px;
+  background: var(--ua-color-border);
+  cursor: col-resize;
+  transition: background 0.15s ease;
+  touch-action: none;
+}
+.ua-splitter-vertical > .ua-splitter-bar {
+  cursor: row-resize;
+}
+.ua-splitter-bar::after {
+  content: '';
+  position: absolute;
+  inset: -4px;
+  /* 扩大命中区：视觉 6px，实际可抓 14px */
+}
+.ua-splitter-bar:hover,
+.ua-splitter-bar.is-dragging,
+.ua-splitter-bar:focus-visible {
+  background: var(--ua-color-accent);
+}
+.ua-splitter-bar:focus-visible {
+  outline: 2px solid var(--ua-color-accent);
+  outline-offset: 1px;
+}
+@media (prefers-reduced-motion: reduce) {
+  .ua-splitter-bar {
+    transition: none;
+  }
+}