feat: milestone scrap — 100 per 10 waves cleared (D239), v2.3.2 Data-driven (scrap.milestone_every / milestone_bonus), whole milestones only. A 30-wave victory now banks 625 scrap instead of 325. Verified: zero-warning build, 8/8 suites (scrap test re-pinned), canary unmoved, gate green. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01YRbTvp64hekcJP3NVHukEU