The hybrid strategy now considers account quota levels when selecting
accounts, preventing any single account from being drained to 0%.
- Add QuotaTracker class to track per-account quota levels
- Exclude accounts with critical quota (<5%) from selection
- Add quota component to scoring formula (weight: 3)
- Fall back to critical accounts when no alternatives exist
- Add 18 new tests for quota-aware selection
Scoring formula: Health×2 + Tokens×5 + Quota×3 + LRU×0.1
An attempt at resolving badrisnarayanan/antigravity-claude-proxy#171