fix(deepresearch): fix ResearchTeamNode error and missing edge from research_team to planner, preventing possible infinite loop

[ichaobuster]

本PR修复以下问题：

• ResearchTeamNode 目前的逻辑会造成进入parallel_executor后可能出现curPlan为null的现象，且可能因此造成research_team_next_node一直为parallel_executor而造成流程进入research_team后死循环。
• 根据 ResearchTeamDispatcher ，默认的情况下路径会进到planner，而 DeepResearchConfiguration 中从research_team出发的conditionalEdge缺少planner的mapping，因此也会造成流程无法运行到END。

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This PR addresses and fixes the following issues:

• ResearchTeamNode's current logic can lead to a scenario where curPlan becomes null after entering the parallel_executor. This can subsequently cause the research_team_next_node to perpetually remain the parallel_executor, resulting in a deadlock once the flow enters the research_team.
• According to the ResearchTeamDispatcher, the default path leads to the planner. However, the DeepResearchConfiguration is missing the planner mapping in the conditional edge starting from the research_team, which also prevents the flow from reaching END.