session naming: archive- prefix convention + cc-ci-report unique-name invariant

- _archive_stale_titles default label is now 'archive-<title> —' (operator
  convention: all archived sessions start with archive- so they sort/filter
  together in the web UI).
- launch-report.py start() archives older cc-ci-report sessions before launch,
  same invariant as upgrader/supervisor (reuses the launch-upgrader helper).
- 33 sessions restyled/archived live; canonical names now unique:
  cc-ci-upgrader (idle finisher), cc-ci-report (generating), cc-ci-supervisor
  (none — only exists during a rescue).

cc-ci-plan/launch-report.py

@@ -70,6 +70,18 @@ def start(mode, date):
             log(f"{SESSION} busy with a report — leaving it"); return
         log(f"{SESSION} exists (idle/leftover) — killing first"); kill_session(); time.sleep(1)
 
+    # Unique-name invariant (same as upgrader/supervisor): archive-rename every older session
+    # titled SESSION so the one this launch creates is the ONLY 'cc-ci-report' in the web UI.
+    # Archived names start with 'archive-' (operator convention 2026-08-04).
+    try:
+        import importlib.util as _ilu
+        _spec = _ilu.spec_from_file_location(
+            "launch_upgrader", os.path.join(os.path.dirname(os.path.realpath(__file__)), "launch-upgrader.py"))
+        _lu = _ilu.module_from_spec(_spec); _spec.loader.exec_module(_lu)
+        _lu._archive_stale_titles(SESSION)
+    except Exception as e:
+        log(f"  (archive-rename skipped: {e})")
+
     kf = Path(LOG_DIR) / f".kickoff-{SESSION}.txt"
     kf.write_text(build_kickoff(date))
     model_flag = f"--model '{MODEL}'" if MODEL else ""