Transmission #049: Skill and character leveling POC in Unity

Implemented the leveling POC: jittered power-of-ten skill thresholds (SkillLevelThresholdEvaluator), per-stat levels and +1 bonuses in ProgressionOrchestrator, overall character level from the sum of skill levels with queued stat-point achievements and Carl-ish toasts, PendingRewardKind on pending rows with claim → loot box or unspent point, six base abilities (start at 1) with TrySpendStatPoint, Skills and Stats inventory tabs (search, placeholder effective skill + disclaimer), and new EditMode tests for thresholds, character math, milestones with mixed rewards, and claim/spend flows.