Handling "one session with only one process"

[noahcui]

In the original code, get_session_chains only removes items from expand_remain when a child process of the current session is found (line 370, which is inside the for loop starting at line 355).

However, there is a potential case where a session contains only a single process and does not spawn any child processes. In such cases, the corresponding process in expand_remain is never discarded.

Since the while True loop (starting at line 384) only exits when expand_current becomes empty—which never happens in this case—this results in an infinite loop.

My solution: Add logic to discard processes from expand_remain if they are not expandable (i.e., they have no children), to ensure the loop can eventually terminate.