Fix stations dropping offline mid-run

A single oversized event — a large image in a prompt, a verbose log dump or a long measurement trace — used to cut a station's live link for the rest of the session, so runs kept passing locally while the dashboard showed the station as offline.

• Fixed the live link dropping when a phase sends an unusually large payload: the event is now shrunk to fit instead of breaking the connection.
• Added readable stand-ins for degraded content — an oversized image becomes a short note explaining the operator screen still shows the full picture, and truncated logs keep their start and end with an explicit marker.
• Kept normal runs untouched: only the payloads that would break the connection are degraded, and phase outcomes always arrive.