Establishes project context for all future agent sessions:
- Architecture overview (no bundler, single-file app pattern)
- Merge-bot validation requirements (node --check, <500KB budget)
- Sequential build order for Nexus v1 (issues #4–#18)
- PR rules: one at a time, squash merge, no manual merges
Refs #36
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>