Re-homed implementation of CUST-WP-0050 Phase 3-4. P1 merges the schema
redesign, data migration, and workstream->workplan rename into one Alembic
window; P2 API/MCP/validation; P3 auto-registration; P4 surfaces & cutover.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>