TCHG-0002 Roadmap, Status, and Parallel Work Coordination

• Added the long-term knowledge-graph roadmap and phase exit criteria.
• Added a current status index with state-specific implementation lanes.
• Defined append-only changelog practice and centralized TCHG reservations.
• Recorded the distinction between strategic direction, current status, and completed historical changes.
• Reserved TCHG-0003 for the Massachusetts CCC end-to-end implementation lane.