chDB embedded engine inherits ClickHouse's default memory limits (max_server_memory_usage based on system RAM, max_server_memory_usage_to_ram_ratio = 0.9), which can cause unexpected query failures in embedded scenarios.

Set both max_server_memory_usage and max_server_memory_usage_to_ram_ratio to 0 (unlimited) in the default _chdb_settings, so chDB does not impose server-level memory caps by default. Users can still override via set_chdb_setting() before the first query.