Keep the node ring lapping while the node is running

The arc was one-shot feedback for an emit, so a node that works for minutes
showed nothing after the first half second. A run now holds the ring on the
node and laps it until the node stops.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SKL7sUgNWhukDEz95vSMQv

frontend/src/components/Flow/flow.css

@@ -109,7 +109,8 @@
 
 /*
  * A node that just published something says so, once, and settles: an arc runs
- * one lap of the rim and goes out.
+ * one lap of the rim and goes out. The same arc, lapping, is a node still at
+ * work.
  *
  * The angle has to be registered to be animatable at all — an unregistered
  * custom property is a token stream, and swapping one for another mid-gradient
@@ -169,6 +170,24 @@
       opacity: 0;
     }
   }
+
+  /*
+   * A node still working keeps the arc going instead: a run lasts as long as it
+   * lasts — a training is minutes — so the lap repeats and never fades out, and
+   * the ring is taken down when the node stops rather than by the animation.
+   * A loop rather than one-shot feedback, so none of the `--duration-*` tokens
+   * fit; the literal is one lap slow enough to read as travel, like the edge
+   * march above.
+   */
+  .node-pulse.node-pulse-run {
+    animation: node-chase 1.2s linear infinite;
+  }
+
+  @keyframes node-chase {
+    to {
+      --node-pulse-angle: 1turn;
+    }
+  }
 }
 
 /* Handles are neutral: the one brand-secondary affordance here is Run. */