Neo4j sync with Dolt canonical state: keep graph in sync after reconciliation

[theinterneti]

Part of #269

After world reconciliation merges a player branch to main: sync the changed Dolt rows back to Neo4j nodes/relationships. Implement DoltToNeo4jSyncer that translates row-level changes to graph mutations.

Acceptance Criteria

• DoltToNeo4jSyncer.sync_from_commit(commit_hash) runs after each reconciliation
• Reads DOLT_DIFF for changed rows since last sync commit
• Translates row changes to Neo4j: UPDATE/CREATE/DELETE nodes and relationships
• Syncer is idempotent (safe to re-run)
• Integration test: reconciliation → sync → Neo4j reflects merged state