feat: add comprehensive zero-config validation system

- Implement self-configuring validation that adapts to system resources
- Add validation for all CRUD operations (add, update, delete, find, relate)
- Auto-configure limits based on available memory (1GB = 10K limit, 8GB = 80K)
- Monitor and auto-tune performance based on query response times
- Fix multiple type filtering with proper anyOf structure
- Enhance type safety by requiring NounType/VerbType enums
- Fix tests to validate correct behavior (no fake implementations)
- Add comprehensive VALIDATION.md documentation
- Update API_REFERENCE.md with validation rules and examples
- Clarify metadata update behavior (null keeps existing, {} clears)

BREAKING CHANGE: getFieldsForType() now requires NounType enum instead of string

Co-Authored-By: Claude <noreply@anthropic.com>

tests/unit/brainy/relate.test.ts

@@ -201,7 +201,7 @@ describe('Brainy.relate()', () => {
         from: entity1Id,
         to: entity2Id,
         type: 'invalidType' as any
-      })).rejects.toThrow('Invalid verb type')
+      })).rejects.toThrow('invalid VerbType')
     })
     
     it('should handle missing required parameters', async () => {