Mem0: Cross-tenant conversation leak via unescaped delimiter collision in session-scope key (_build_session_scope)

Summary buildsessionscope in mem0/memory/main.py builds the conversation-history scope key used to fetch/store the last N raw messages by naively joining caller-supplied userid/agentid/runid values with unescaped & and = delimiters: def buildsessionscopefilters: parts = for key in sorted"userid",...