fix: infer compound node color from descendants when no own overlay state

Path containers (EIP_WHEN, EIP_OTHERWISE, etc.) don't have their own
processor records, so they never get an overlay entry. Now inferred
from descendants: green if any descendant executed, red if any failed.
Gated (amber) only when no descendants executed at all.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/ProcessDiagram/CompoundNode.tsx

@@ -68,18 +68,19 @@ export function CompoundNode({
 
   // Execution overlay state for this compound
   const ownState = node.id ? executionOverlay?.get(node.id) : undefined;
-  const hasExecutedChild = ownState && hasExecutedDescendant(node, executionOverlay);
+  const executedDescendant = hasExecutedDescendant(node, executionOverlay);
   const isCompleted = ownState?.status === 'COMPLETED';
   const isFailed = ownState?.status === 'FAILED';
+  const descendantFailed = executedDescendant && hasFailedDescendant(node, executionOverlay);
 
-  // Gated = gate processor (filter/idempotent) blocked all children from executing
-  const isGated = ownState && !hasExecutedChild
+  // Gated = gate processor blocked all children from executing
+  const isGated = ownState && !executedDescendant
     && (ownState.filterMatched === false || ownState.duplicateMessage === true);
 
-  // Color priority: gated (amber) > failed (red) > completed (green) > default
+  // Color: own status first, then infer from descendants (for path containers like when/otherwise)
   const effectiveColor = isGated ? 'var(--amber)'
-    : isFailed ? '#C0392B'
-    : isCompleted ? '#3D7C47'
+    : isFailed || descendantFailed ? '#C0392B'
+    : isCompleted || executedDescendant ? '#3D7C47'
     : color;
 
   // Dim compound when overlay is active but neither the compound nor any
@@ -295,3 +296,18 @@ function hasExecutedDescendant(
   }
   return false;
 }
+
+function hasFailedDescendant(
+  node: DiagramNodeType,
+  overlay?: Map<string, NodeExecutionState>,
+): boolean {
+  if (!overlay || !node.children) return false;
+  for (const child of node.children) {
+    if (child.id) {
+      const state = overlay.get(child.id);
+      if (state?.status === 'FAILED') return true;
+    }
+    if (child.children && hasFailedDescendant(child, overlay)) return true;
+  }
+  return false;
+}