Top-Slot Burn and Discarded-Agent Cleanup

Race System

• Agents discarded during a race are no longer counted in that race's finisher set, so legitimate finishers' rank positions don't depend on whether other agents were removed mid-race.

Emissions

• When no admin-designated top miner is set, the top-25% emission slot now burns instead of falling back to the prior race winner. The prior fallback could keep paying emission to a miner whose agent had since been beaten or eliminated.

Anti-Cheating

• Cheating detection coverage expanded.