Implements §16.15 progressive disclosure system that reveals advanced
UI features gradually based on user engagement (XP tracked via localStorage).
Features:
- XP tracking system stored in localStorage
- reveal(featureKey) / isRevealed(featureKey) API
- 9 XP-gated features (event timeline, view modes, follow camera, etc.)
- Action-based features (predictions, sandbox, embed) unlocked by specific user actions
- Power user override to show all controls
- Engagement tracking (30+ second replay watch = 1 XP)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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