`team.invest()` doesn't set action.llm.cost_manager

[azurewtl]

Bug description

team = Team(context=ctx)
team.invest(investment=args.cost)
team.hire(
    [
        Manager(),
        Searcher(),
        Researcher(),
        Editor(),
        Reviewer(),
        Human(is_human=True),
    ]
)

team.invest() doesn't set action.llm.cost_manager,

Bug solved method I think ContextMixin should be implemented as a singleton? When instanciate new Action, it subclass ContextMixin. And I think the problem might be in this property. line = 78-83

@property
def context(self) -> Context:
    """Role context: role context > context"""
    if self.private_context:
        return self.private_context
    return Context()

It returns a new context regardless of what cost_manager you set from team.invest(), because when we get llm from action instance, it use self.context line 94-95

if not self.private_llm:
    self.private_llm = self.context.llm_with_cost_manager_from_llm_config(self.config.llm)

Environment information

• LLM type and model name:
• System version: metagpt 0.7.6
• Python version: python 3.10