fix: actually wire loop_session into the snapshot payload

The prior commit imported query_loop_session but a botched idempotency
guard skipped inserting the snapshot field (the import string itself
matched the 'already present' check) — ruff unused-import failed CI and
the stale-session banner had no data. Field added; banner live.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

api/main.py

@@ -329,6 +329,9 @@ class DashboardState:
                     "daily": query_daily_performance(store),
                     "risk": query_risk_state(store, for_date=for_date),
                     "triggers": query_armed_triggers(store) if is_live else {"triggers": [], "armed": 0},
+                    # loop session identity + day-2 staleness alarm (memory-only
+                    # daily flags survive midnight only to silently block entries)
+                    "loop_session": query_loop_session(store) if is_live else {},
                     "equity_curve": query_equity_curve(store, for_date=for_date),
                     "catalyst": catalyst,
                     "catalyst_engine": _catalyst_engine(store, catalyst) if is_live else {},