Refactor documentation structure and improve wording

[TeaNguyen]

Summary

• Split the single syntax page into three focused sub-pages:
  • Core Database Markup — all SQL-mapped constructs
  • Enrichment & Visualization — diagram/wiki-only features
  • Language Reference — language-level constructs
• Fix typo, improve wording

Checklist

Please check directly on the box once each of these are done

• Documentation (if necessary)
• Lint Checks Passed
• Unit Tests Passed
• Coverage Tests Passed
• Integration Tests Passed
• Code Review