iter(g47): 新增 cascader 级联选择组件

packages/skin/ui/ui.css

@@ -2546,3 +2546,128 @@ button.ua-step-dot:hover {
     transition: none;
   }
 }
+.ua-cascader {
+  position: relative;
+  display: inline-block;
+  min-width: 220px;
+}
+.ua-cascader-trigger {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: var(--ua-space-1);
+  width: 100%;
+  padding: 8px var(--ua-space-2);
+  font-size: var(--ua-font-size-sm);
+  color: var(--ua-color-text);
+  background: var(--ua-color-surface);
+  border: 1px solid var(--ua-color-border);
+  border-radius: var(--ua-radius-sm);
+  cursor: pointer;
+  transition: border-color 0.15s ease, box-shadow 0.15s ease;
+}
+.ua-cascader-trigger:hover {
+  border-color: var(--ua-color-accent);
+}
+.ua-cascader-trigger:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+.ua-cascader.ua-open .ua-cascader-trigger {
+  border-color: var(--ua-color-accent);
+  box-shadow: 0 0 0 3px color-mix(in srgb, var(--ua-color-accent) 18%, transparent);
+}
+.ua-cascader-value.is-empty {
+  color: var(--ua-color-text-muted);
+}
+.ua-cascader-caret {
+  font-size: 10px;
+  color: var(--ua-color-text-muted);
+  transition: transform 0.15s ease;
+}
+.ua-cascader.ua-open .ua-cascader-caret {
+  transform: rotate(180deg);
+}
+.ua-cascader-pop {
+  position: absolute;
+  z-index: 40;
+  display: none;
+  margin-top: 6px;
+  border: 1px solid var(--ua-color-border);
+  border-radius: var(--ua-radius-md);
+  background: var(--ua-color-surface);
+  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.18);
+  overflow: hidden;
+}
+.ua-cascader-pop.ua-open {
+  display: block;
+  animation: ua-cascader-in 0.15s ease both;
+}
+.ua-cascader-pop.is-flip {
+  margin-top: 0;
+  margin-bottom: 6px;
+}
+.ua-cascader-panels {
+  display: flex;
+  align-items: stretch;
+}
+.ua-cascader-col {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  min-width: 132px;
+  max-height: 220px;
+  margin: 0;
+  padding: var(--ua-space-1);
+  overflow: auto;
+  list-style: none;
+  border-right: 1px solid var(--ua-color-border);
+}
+.ua-cascader-col:last-child {
+  border-right: none;
+}
+.ua-cascader-opt {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: var(--ua-space-1);
+  padding: 6px var(--ua-space-1);
+  font-size: var(--ua-font-size-sm);
+  color: var(--ua-color-text);
+  background: transparent;
+  border: none;
+  border-radius: var(--ua-radius-sm);
+  text-align: left;
+  cursor: pointer;
+  transition: background 0.15s ease, color 0.15s ease;
+}
+.ua-cascader-opt:hover:not(:disabled),
+.ua-cascader-opt.is-active {
+  background: color-mix(in srgb, var(--ua-color-accent) 10%, transparent);
+}
+.ua-cascader-opt.is-picked {
+  color: var(--ua-color-accent);
+  font-weight: 600;
+}
+.ua-cascader-opt:disabled {
+  opacity: 0.45;
+  cursor: not-allowed;
+}
+.ua-cascader-opt:focus-visible {
+  outline: 2px solid var(--ua-color-accent);
+  outline-offset: -2px;
+}
+.ua-cascader-arrow {
+  color: var(--ua-color-text-muted);
+  font-size: 10px;
+}
+@keyframes ua-cascader-in {
+  from { opacity: 0; transform: translateY(-4px); }
+  to   { opacity: 1; transform: translateY(0); }
+}
+@media (prefers-reduced-motion: reduce) {
+  .ua-cascader-pop.ua-open { animation: none; }
+  .ua-cascader-trigger,
+  .ua-cascader-caret,
+  .ua-cascader-opt { transition: none; }
+}