Test 2: Checking deep merge of nested objects...
ERROR: Deep merge failed:
  - server.host should be 'localhost' (preserved), got '0.0.0.0'
  - server.timeout should be 30 (preserved), got None
  - database.type should be 'postgres' (preserved)
  - database.pool.max should be 20 (overridden)
  - database.pool.min should be 2 (preserved)
  - database.pool.idle should exist (added)