[eric] workflows: stop endpoint + last_tool_label live subtitle for RunningView

frontend/src/app/pages/Workflows/WorkflowCardLiveViews.tsx

@@ -151,10 +151,10 @@ export function RunningView({ workflow, steps, runs, mode = 'card' }: {
   const completeCount = statuses.filter((s) => s === 'done').length;
   const total = steps.length;
 
-  // Tool-call subtitle for the active step. The backend will emit this on
-  // workflow:run as `last_tool_label` once slice 5 lands; until then we
-  // surface a soft placeholder so the row never feels empty.
-  const activeSubtitle = (run as unknown as { last_tool_label?: string })?.last_tool_label || null;
+  // Tool-call subtitle for the active step. Backend polls the session's
+  // messages at 1.5s cadence and broadcasts on workflow:run as the agent
+  // makes new tool calls. See executor.py _watch_tool_calls.
+  const activeSubtitle = run?.last_tool_label || null;
   const activeDuration = formatLiveDuration(run);
 
   const isLinked = mode === 'sidecar-linked' && card?.sidecarKind === 'watching';

frontend/src/shared/state/workflowsSlice.ts

@@ -90,6 +90,8 @@ export interface WorkflowRun {
   error: string | null;
   cost_usd: number;
   triggered_by: 'schedule' | 'manual' | 'retry';
+  /** Live "what's the agent doing" subtitle while status is 'running'. */
+  last_tool_label?: string | null;
 }
 
 /** Transient view-only state per card; position lives in dashboardLayoutSlice.workflowCards. */