fix(plan): ensure changeHook receives finished plan instead of null in finishPlan()#1400

LearningGp merged 6 commits into

agentscope-ai:mainagentscope-ai/agentscope-java:mainfrom

birdie7761:fix/finishplan-hook-nullbirdie7761/agentscope-java:fix/finishplan-hook-nullCopy head branch name to clipboard