fix: finalize session after memory promotion

frontend/src/shell/AppShell.tsx

@@ -177,9 +177,13 @@ export function AppShell() {
   // stopSession already does, and this effect must stay side-effect-free on the
   // backend if the session is already inactive.
   useEffect(() => {
-    if (lastSystemEvent?.type === "system_event" && (lastSystemEvent as any).event === "session_exit") {
-      stopSession();
-    }
+    if (lastSystemEvent?.type !== "system_event") return;
+    const ev = (lastSystemEvent as any).event;
+    if (ev === "session_exit") stopSession();
+    // The final workflow turn ends with the session already finalized on disk:
+    // refetch now instead of waiting for the 10s poll, so the completed state
+    // (and the new-session invite below the transcript) appears immediately.
+    if (ev === "agent_end") refresh();
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [lastSystemEvent]);
 
@@ -241,6 +245,17 @@ export function AppShell() {
               <>
                 <CentralStatus working={working} />
                 <WidgetHost sessionId={activeSessionId} />
+                {finalized && !agentActive && (
+                  <div className="rounded-2xl border border-border/80 bg-card p-5 text-center shadow-md">
+                    <p className="text-sm text-muted-foreground">
+                      Session completed and finalized — the SQL and all phase
+                      documents are saved.
+                    </p>
+                    <Button className="mt-3" onClick={startNewSession}>
+                      Start a new question
+                    </Button>
+                  </div>
+                )}
               </>
             ) : (
               <EmptyState />