Race Polish & Code Quality

Race System

• Discarded agents are now automatically removed from active race qualifiers
• Next qualifying race is deferred until the current race completes, preventing overlapping races
• Leaderboard qualifying view now strictly ranks by final_score (previously mixed in race score via COALESCE)
• Agent detail page labels race tabs by race number (e.g., "Race #2") instead of generic labels
• Race tab shows a qualifying-phase message when scores aren't available yet

Agent Detail

• Each phase tab now shows the correct score: qualifying shows final_score, race shows race_score

Backend

• Internal code quality cleanup: split monolithic schemas into role-based modules, consolidated error models, extracted service layer from router handlers