[bug] `new_text_message()` may create messages with empty contents

[IthacaDream]

Issue:

• new_text_message() may create messages with empty contents

MOSShell/src/ghoshell_moss/message/utils.py

Lines 9 to 15 in 02c74f3

	def new_text_message(content: str, *, role: str | Role = "") -> Message:
	"""
	创建一个系统消息.
	"""
	meta = MessageMeta(role=str(role))
	obj = Text(text=content)
	return Message(meta=meta).as_completed([obj.to_content()])

Description:

new_text_message() builds a Message with the default seq="completed" and then calls as_completed(contents).
Since Message.as_completed() returns early when seq is already "completed", the provided contents are ignored and the resulting message can have missing/empty contents.
This breaks downstream consumers that expect context messages to contain serialized content parts.

MOSShell/src/ghoshell_moss/message/abcd.py

Lines 562 to 571 in 02c74f3

	def as_completed(self, contents: list[Content] | None = None) -> Self:
	"""
	基于当前数据, 生成一个 尾包.
	常见用法:
	>>> msg = Message.new().as_completed(contents)
	>>> # 复制一个新的尾包.
	>>> copy_msg = msg.get_copy().as_completed()
	"""
	if self.seq == "completed":
	return self

Repro Steps:

Use the following test function:

    def test_new_text_message_creates_completed_message() -> None:
        msg = new_text_message("hello", role="system")
        assert msg.role == Role.SYSTEM.value
        assert msg.seq == "completed"
>       assert msg.contents is not None
E       AssertionError: assert None is not None