Show live account snapshot in maker cycle output

[wjllance]

Summary

• Add the live exchange account snapshot to maker cycle output in both human-readable and JSON modes.
• Include balance, equity, available, and upnl while keeping them distinct from the maker session’s own pnl.
• Document the new live-only account fields and add unit coverage for JSON shaping and amount formatting.

Testing

• Unit tests added for account snapshot serialization and compact amount formatting.
• Not run (not requested).