supervisor: unique cc-ci-supervisor web-UI name (same invariant as the upgrader)

_archive_stale_titles() generalized to (title, label); launch-supervisor's
spawn_supervisor() archives every older 'cc-ci-supervisor' session before
launching, so exactly one session carries the name. 11 historical supervisor
sessions archive-renamed live ('supervisor archive — <date> <time>').

cc-ci-plan/launch-supervisor.py

@@ -98,6 +98,12 @@ def spawn_supervisor(sid, reason):
     Path(LOG_DIR).mkdir(parents=True, exist_ok=True)
     if _sup_alive():
         _sup_kill(); time.sleep(1)
+    # Unique-name invariant (same as the upgrader): archive-rename every older session titled
+    # SUP_SESSION so the one this launch creates is the ONLY 'cc-ci-supervisor' in the web UI.
+    try:
+        lu._archive_stale_titles(SUP_SESSION, "supervisor archive —")
+    except Exception:
+        pass
     kf = Path(LOG_DIR) / f".kickoff-{SUP_SESSION}.txt"
     kf.write_text(build_kickoff(sid, reason))
     share = "--share" if OPENCODE_SHARE else ""