story-kit: create 138_bug_no_heartbeat_to_detect_stale_websocket_connections

.story_kit/work/1_upcoming/138_bug_no_heartbeat_to_detect_stale_websocket_connections.md

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+---
+name: "No heartbeat to detect stale WebSocket connections"
+---
+
+# Bug 138: No heartbeat to detect stale WebSocket connections
+
+## Description
+
+The WebSocket client in frontend/src/api/client.ts only reconnects when the onclose event fires. If the connection half-closes (appears open but stops receiving data), onclose never fires and reconnection never happens. There is no ping/pong heartbeat mechanism to detect this state.
+
+## How to Reproduce
+
+1. Open the web UI and establish a WebSocket connection
+2. Wait for a network disruption or half-close scenario
+3. The connection appears open but stops delivering messages
+4. No reconnection is attempted
+
+## Actual Result
+
+The frontend keeps a dead WebSocket open indefinitely with no way to detect it has stopped receiving data. UI becomes permanently stale until manual refresh.
+
+## Expected Result
+
+A heartbeat mechanism should detect stale connections and trigger automatic reconnection.
+
+## Acceptance Criteria
+
+- [ ] WebSocket client implements a periodic heartbeat/ping to detect stale connections
+- [ ] Stale connections are automatically closed and reconnected
+- [ ] Server responds to ping frames or implements server-side keepalive