Move the canonical working-agreements file to core/CLAUDE.md (preserving
history) and leave a thin root CLAUDE.md pin that imports it so the
invariants still auto-load at the repo root. Update ONBOARDING.md's stale
docs/ paths to core/docs/. The move also fixes the core/src/*/AGENTS.md
links that pointed at ../../CLAUDE.md.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015hmgREHNsxYCuim33yUF2c
