feat(ui): add activity indicator governance

registry/components.json

@@ -33,6 +33,22 @@
         "Destructive actions remain neutral until confirmation unless danger is the principal message."
       ]
     },
+    {
+      "id": "activity-indicator",
+      "status": "baseline",
+      "package": "@nodedc/ui-react",
+      "exports": ["ActivityIndicator", "ActivityIndicatorProps", "ActivityIndicatorSize"],
+      "domContract": ["nodedc-activity-indicator"],
+      "summary": "Theme-independent indeterminate progress indicator for inline operations and pending action controls.",
+      "variants": ["default", "compact"],
+      "behavior": ["decorative by default", "optional status semantics", "static reduced-motion presentation"],
+      "rules": [
+        "Use compact inside a Button icon slot and default for standalone inline progress.",
+        "The process owner exposes aria-busy and visible pending copy; provide label only when the indicator itself is the status announcement.",
+        "The component never owns operation state, timing or completion.",
+        "Reduced-motion preferences stop rotation without hiding the pending-state affordance."
+      ]
+    },
     {
       "id": "field",
       "status": "baseline",