feat(ui): add activity indicator governance

packages/ui-core/styles.css

@@ -211,6 +211,30 @@
   transform: scale(var(--nodedc-icon-glyph-scale));
 }
 
+.nodedc-activity-indicator {
+  display: inline-block;
+  width: 1.125rem;
+  height: 1.125rem;
+  flex: 0 0 auto;
+  box-sizing: border-box;
+  border: 2px solid currentColor;
+  border-inline-end-color: transparent;
+  border-radius: var(--nodedc-radius-circle);
+  color: inherit;
+  opacity: 0.78;
+  animation: nodedc-activity-indicator-spin 780ms linear infinite;
+}
+
+.nodedc-activity-indicator[data-size="compact"] {
+  width: 0.875rem;
+  height: 0.875rem;
+  border-width: 1.5px;
+}
+
+@keyframes nodedc-activity-indicator-spin {
+  to { transform: rotate(360deg); }
+}
+
 .nodedc-icon-button {
   display: inline-grid;
   width: var(--nodedc-icon-button-size);
@@ -3585,6 +3609,7 @@ textarea.nodedc-field__control {
 }
 
 @media (prefers-reduced-motion: reduce) {
+  .nodedc-activity-indicator,
   .nodedc-dropdown-surface,
   .nodedc-overlay,
   .nodedc-window,

packages/ui-react/src/ActivityIndicator.tsx

@@ -0,0 +1,32 @@
+import type { HTMLAttributes } from "react";
+import { cn } from "./cn.js";
+
+export type ActivityIndicatorSize = "default" | "compact";
+
+export interface ActivityIndicatorProps extends Omit<
+  HTMLAttributes<HTMLSpanElement>,
+  "aria-hidden" | "aria-label" | "children" | "role"
+> {
+  size?: ActivityIndicatorSize;
+  label?: string;
+}
+
+export function ActivityIndicator({
+  size = "default",
+  label,
+  className,
+  ...props
+}: ActivityIndicatorProps) {
+  const accessibleLabel = label?.trim() || undefined;
+
+  return (
+    <span
+      {...props}
+      className={cn("nodedc-activity-indicator", className)}
+      data-size={size === "default" ? undefined : size}
+      role={accessibleLabel ? "status" : undefined}
+      aria-label={accessibleLabel}
+      aria-hidden={accessibleLabel ? undefined : "true"}
+    />
+  );
+}

packages/ui-react/src/index.ts

@@ -1,4 +1,5 @@
 export * from "./AppHeader.js";
+export * from "./ActivityIndicator.js";
 export * from "./AdminNavigationPanel.js";
 export * from "./ApplicationShell.js";
 export * from "./ApplicationSidePanel.js";