Address review feedback: revert KillSession back to KillSessionWithProcesses
in stopSession() to properly terminate all child processes.
KillSessionWithProcesses recursively finds and terminates descendant processes
with SIGTERM/SIGKILL, preventing orphaned Claude/node processes that can
survive tmux session kills.
The orphan detection in verifyShutdown() remains as a helpful warning but
shouldn't replace proper process termination.
d2f7dbd3ae