fix(FN-2872): reduce blocked-task log noise and clarify routing details

- Add a Node Routing section in TaskDetailModal showing override, effective node/source, unavailable-node policy, and blocking reason
- Remove duplicate blocked-state heartbeat log output when the blocked reason has not changed
- Silence runtime onBlocked logging to avoid repeated blocked-task log spam

packages/dashboard/app/components/TaskDetailModal.tsx

@@ -1629,6 +1629,31 @@ export function TaskDetailModal({
             </div>
           )}
           <MergeDetails task={task} />
+          <div className="detail-section">
+            <h4>Node Routing</h4>
+            <dl className="detail-source-grid">
+              <div>
+                <dt>Task Override</dt>
+                <dd>{task.nodeId ?? <span className="detail-source-empty">(none)</span>}</dd>
+              </div>
+              <div>
+                <dt>Effective Node</dt>
+                <dd>{(task as Task & { effectiveNodeId?: string }).effectiveNodeId ?? "local execution"}</dd>
+              </div>
+              <div>
+                <dt>Routing Source</dt>
+                <dd>{(task as Task & { effectiveNodeSource?: string }).effectiveNodeSource ?? "local"}</dd>
+              </div>
+              <div>
+                <dt>Unavailable Node Policy</dt>
+                <dd>{(settings as Settings & { unavailableNodePolicy?: string } | undefined)?.unavailableNodePolicy ?? "block"}</dd>
+              </div>
+              <div>
+                <dt>Blocking Reason</dt>
+                <dd>{((task as Task & { blockedReason?: string; statusReason?: string }).blockedReason || (task as Task & { statusReason?: string }).statusReason) ?? <span className="detail-source-empty">(not blocked)</span>}</dd>
+              </div>
+            </dl>
+          </div>
           {task.sourceIssue && (
             <div className="detail-section detail-source-section">
               <h4>Source Issue</h4>