The root cause: checkpoint handler queued .trade via say_delayed, but
monop sends '-- Command:' before processing the trade. The old handler
reset in_trade and queued .roll, so both commands got sent.
Fix: checkpoint handler no longer sends commands. The -- Command:
prompt is where the bot decides to trade or roll, matching how monop
actually works (-- Command: is the interactive prompt).
Also: no trades while in jail (jail has no -- Command: before roll).
Updated all tests to reflect the new flow.
