Mastery Map page — Mastery Definition plan §5.

Reachable via direct URL only; not linked from primary nav until the S50 measurement window clears (≥ 2026-05-01) per plan §8 Week 1. Self-only data — JS hydration calls /api/learning/ mastery/summary which is require_auth-gated; anonymous users get a sign-in prompt rendered client-side.

Pre-v51: page works today, just shows attempted/familiar/ proficient counts. Post-v51 activation: same page surfaces Mastered + Enduring without server changes.