iter(g33): 新增 upload 文件选择组件

packages/skin/ui/ui.css

@@ -2195,3 +2195,90 @@ button.ua-step-dot:hover {
     transition: none;
   }
 }
+
+/* —— 文件选择 —— */
+.ua-upload {
+  display: flex;
+  flex-direction: column;
+  gap: var(--ua-space-2);
+  width: 100%;
+  max-width: 360px;
+}
+.ua-upload-zone {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: var(--ua-space-1);
+  padding: var(--ua-space-4) var(--ua-space-3);
+  border: 1px dashed var(--ua-color-border);
+  border-radius: var(--ua-radius-md);
+  background: var(--ua-color-surface);
+  color: var(--ua-color-text-muted);
+  cursor: pointer;
+  outline: none;
+  transition: border-color 0.15s ease, background 0.15s ease;
+}
+.ua-upload-zone:hover,
+.ua-upload-over {
+  border-color: var(--ua-color-accent);
+  background: color-mix(in srgb, var(--ua-color-accent) 6%, transparent);
+}
+.ua-upload-zone:focus-visible {
+  box-shadow: 0 0 0 2px color-mix(in srgb, var(--ua-color-accent) 40%, transparent);
+}
+.ua-upload-disabled {
+  cursor: not-allowed;
+  opacity: 0.6;
+}
+.ua-upload-icon {
+  font-size: var(--ua-font-size-lg);
+  color: var(--ua-color-accent);
+}
+.ua-upload-hint {
+  font-size: var(--ua-font-size-sm);
+}
+.ua-upload-input {
+  display: none; /* 原生选择器只作为能力载体，界面自绘 */
+}
+.ua-upload-list {
+  display: flex;
+  flex-direction: column;
+  gap: var(--ua-space-1);
+}
+.ua-upload-item {
+  display: flex;
+  align-items: center;
+  gap: var(--ua-space-2);
+  padding: var(--ua-space-1) var(--ua-space-2);
+  border: 1px solid var(--ua-color-border);
+  border-radius: var(--ua-radius-sm);
+  font-size: var(--ua-font-size-sm);
+}
+.ua-upload-name {
+  flex: 1;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  color: var(--ua-color-text);
+}
+.ua-upload-size {
+  color: var(--ua-color-text-muted);
+}
+.ua-upload-remove {
+  border: none;
+  background: none;
+  color: var(--ua-color-text-muted);
+  cursor: pointer;
+  line-height: 1;
+  padding: 0 2px;
+}
+.ua-upload-remove:hover {
+  color: var(--ua-color-danger);
+}
+@media (prefers-reduced-motion: reduce) {
+  .ua-upload-zone {
+    transition: none;
+  }
+}