iter(g132): 新增 @提及输入 mentions

packages/skin/ui/ui.css

@@ -4151,3 +4151,80 @@ h5.ua-type-title { font-size: var(--ua-font-size-md); }
     transform: none;
   }
 }
+
+/* —— @提及输入：弹层贴输入框下沿，候选行高亮走淡色底 —— */
+.ua-mentions {
+  position: relative;
+  display: inline-block;
+  width: 100%;
+}
+.ua-mentions-input {
+  width: 100%;
+  box-sizing: border-box;
+  padding: var(--ua-space-2) var(--ua-space-3);
+  border: 1px solid var(--ua-color-border);
+  border-radius: var(--ua-radius-md);
+  background: var(--ua-color-surface);
+  color: var(--ua-color-text);
+  font: inherit;
+  font-size: var(--ua-font-size-md);
+  line-height: 1.6;
+  resize: vertical;
+  transition: border-color 0.15s ease, box-shadow 0.15s ease;
+}
+.ua-mentions-input:focus {
+  outline: none;
+  border-color: var(--ua-color-accent);
+  box-shadow: 0 0 0 3px color-mix(in srgb, var(--ua-color-accent) 22%, transparent);
+}
+.ua-mentions-pop {
+  position: absolute;
+  left: 0;
+  right: 0;
+  top: calc(100% + 4px);
+  z-index: 30;
+  display: none;
+  max-height: 220px;
+  overflow-y: auto;
+  padding: var(--ua-space-1);
+  border: 1px solid var(--ua-color-border);
+  border-radius: var(--ua-radius-md);
+  background: var(--ua-color-surface);
+  box-shadow: 0 12px 28px color-mix(in srgb, var(--ua-color-text) 16%, transparent);
+}
+.ua-mentions.is-open .ua-mentions-pop {
+  display: block;
+  animation: ua-mentions-in 0.15s ease;
+}
+.ua-mentions-item {
+  display: flex;
+  align-items: baseline;
+  gap: var(--ua-space-2);
+  padding: var(--ua-space-2) var(--ua-space-2);
+  border-radius: var(--ua-radius-sm);
+  cursor: pointer;
+  transition: background 0.15s ease;
+}
+.ua-mentions-item.is-active {
+  background: color-mix(in srgb, var(--ua-color-accent) 10%, transparent); /* 选中态低视觉比重 */
+}
+.ua-mentions-name {
+  color: var(--ua-color-text);
+}
+.ua-mentions-desc {
+  color: var(--ua-color-text-muted);
+  font-size: var(--ua-font-size-sm);
+}
+@keyframes ua-mentions-in {
+  from { opacity: 0; transform: translateY(-4px); }
+  to { opacity: 1; transform: none; }
+}
+@media (prefers-reduced-motion: reduce) {
+  .ua-mentions.is-open .ua-mentions-pop {
+    animation: none;
+  }
+  .ua-mentions-input,
+  .ua-mentions-item {
+    transition: none;
+  }
+}