Method with_os

tutorials/18_design_patterns_for_agents.py:415–418

(self, name: str, version: str)

        # 对应 prompt.rs:108-113
        # pub fn with_os(mut self, name, version) -> Self { ... self }
        def with_os(self, name: str, version: str) -> SystemPromptBuilder:
            self._os_name = name
            self._os_version = version
            return self  # 返回 self → 支持链式调用

        # 对应 prompt.rs:101-106
        def with_style(self, name: str, prompt: str) -> SystemPromptBuilder: