Wraps _session_cache mutations in threading.RLock. Without this, concurrent
gateway sessions (e.g., Telegram + Discord hitting Honcho at the same time)
can race on the cache and silently lose conclusions or memory writes.
Adopted from #13510 by @hekaru-agent; the off-topic cron/jobs.py cleanup
hunk from that PR is dropped here for scope isolation. Resolved a small
conflict with the pinPeerName guard (kept both).
dad0217450