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-upgrader.py

@@ -293,7 +293,9 @@ def _archive_stale_titles(title=None, label=None):
     title lookup in _session_id() unambiguous. Old runs stay browsable under
     '<label> — <date>'. Also used by launch-supervisor.py for its own session name."""
     title = title or SESSION
-    label = label or ("upgrader archive — weekly" if title == "cc-ci-upgrader" else f"{title} archive —")
+    # Archive names always start with 'archive-' (operator convention 2026-08-04) so they
+    # sort/filter together in the web UI: 'archive-<original-title> — <date>'.
+    label = label or f"archive-{title} —"
     rows = _server_get("/session") or []
     rows = rows if isinstance(rows, list) else rows.get("data", [])
     for s in rows: