iter(g08): 新增 segmented 分段控制器组件

packages/skin/ui/ui.css

@@ -1754,3 +1754,65 @@ button.ua-step-dot:hover {
     transition: none !important;
   }
 }
+
+/* —— 分段控制器：胶囊容器 + 滑动滑块，选中态低视觉比重 —— */
+.ua-segmented {
+  position: relative;
+  display: inline-flex;
+  border: 1px solid var(--ua-color-border);
+  border-radius: 999px;
+  background: color-mix(in srgb, var(--ua-color-text) 4%, transparent);
+  overflow: hidden;
+}
+.ua-seg-thumb {
+  position: absolute;
+  top: 0;
+  left: 0;
+  height: 100%;
+  border-radius: 999px;
+  background: var(--ua-color-bg);
+  box-shadow: 0 1px 4px color-mix(in srgb, var(--ua-color-text) 12%, transparent);
+  transition: transform 0.18s ease, width 0.18s ease;
+  pointer-events: none;
+}
+.ua-seg-btn {
+  position: relative;
+  z-index: 1;
+  padding: 5px 14px;
+  border: 0;
+  border-radius: 999px;
+  background: transparent;
+  color: var(--ua-color-text-muted);
+  font-size: var(--ua-font-size-md);
+  cursor: pointer;
+  transition: color 0.15s;
+  white-space: nowrap;
+}
+.ua-seg-btn:hover:not(:disabled) {
+  color: var(--ua-color-text);
+}
+.ua-seg-btn:focus-visible {
+  outline: 2px solid var(--ua-color-accent);
+  outline-offset: -2px;
+}
+.ua-seg-btn.is-active {
+  color: var(--ua-color-accent);
+  font-weight: 600;
+}
+.ua-seg-btn:disabled {
+  color: color-mix(in srgb, var(--ua-color-text-muted) 45%, transparent);
+  cursor: not-allowed;
+}
+.ua-segmented-sm .ua-seg-btn {
+  padding: 3px 10px;
+  font-size: var(--ua-font-size-sm);
+}
+.ua-segmented.is-disabled {
+  opacity: 0.6;
+}
+@media (prefers-reduced-motion: reduce) {
+  .ua-seg-thumb,
+  .ua-seg-btn {
+    transition: none !important;
+  }
+}