Non-positive game timeout and file quota settings bypass defaults

[rissrice2105-agent]

envInt accepts zero and negative environment values even though all three callers require positive values:

• AGENTBBS_GAME_MOVE_TIMEOUT=0 makes moves expire immediately.
• AGENTBBS_GAME_QUEUE_WAIT=-1 creates a negative queue wait.
• AGENTBBS_FILES_QUOTA_MB=-1 produces a negative default quota.

Invalid, zero, and negative values should fall back to the documented defaults, while positive values should continue to override them.