Background/remote task completions collapse into one line, and remote task logs are kept

Consecutive completion notices of the same kind now collapse into a single summary line instead of printing one line per finished remote task, and only bash completions are registered in the background-command map. Separately, streamed remote session events are now accumulated per task in a new remoteSessionLogs map, tracking event count, tool call count, agent spawn count, last tool use, and a bounded tail of output; the log is cleared on reset and dropped when its task is evicted.