fix: update security test expectations for enhanced validation messages

- Update flexible-instance-security.test.ts to match new specific error messages
- Update flexible-instance-security-advanced.test.ts for enhanced validation
- Improve security by removing sensitive data from validation error messages
- All 37 security tests now passing

Fixes CI test failures after validation enhancement

🤖 Generated with Claude Code

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

tests/unit/flexible-instance-security-advanced.test.ts

@@ -48,7 +48,7 @@ describe('Advanced Security and Error Handling Tests', () => {
 
       // URL should be invalid due to special characters
       expect(validation.valid).toBe(false);
-      expect(validation.errors).toContain('Invalid n8nApiUrl format');
+      expect(validation.errors?.some(error => error.startsWith('Invalid n8nApiUrl:'))).toBe(true);
     });
 
     it('should handle XSS attempts in context fields', () => {
@@ -304,7 +304,7 @@ describe('Advanced Security and Error Handling Tests', () => {
       const validation = validateInstanceContext(sensitiveContext);
 
       expect(validation.valid).toBe(false);
-      expect(validation.errors).toContain('Invalid n8nApiUrl format');
+      expect(validation.errors?.some(error => error.startsWith('Invalid n8nApiUrl:'))).toBe(true);
 
       // Should not contain the actual invalid URL
       const errorData = JSON.stringify(validation);