d4b9fa1c29
The connectivity probe parsed the full /probe device model every 5 s and discarded it. It now calls a new IMTConnectAgentClient.PingAsync: one GET /probe read with ResponseHeadersRead and a status check; the body is dropped unread. Same failure surface as ProbeAsync (the default implementation delegates to it). The probe-tick tests now count pings and pin that no tick issues a full /probe; the shutdown test's absence assertion gained a positive control. Refs #743 Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT