feat(frontend): SessionMenu kebab + NavSessions prop-driven; AppShell owns sessions query

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/shell/AppShell.tsx

@@ -7,7 +7,9 @@ import { SteerInput, ComposerFooter } from "./SteerInput";
 import { WorkflowBar } from "./WorkflowBar";
 import { Button } from "../components/ui/button";
 import { Toaster } from "../components/ui/sonner";
-import { closeSession } from "../api/sessions";
+import { closeSession, listSessions, resumeSession } from "../api/sessions";
+import type { SessionSummary } from "../api/types";
+import { useQuery } from "@tanstack/react-query";
 import { useRef, useState } from "react";
 
 /**
@@ -18,6 +20,9 @@ import { useRef, useState } from "react";
  */
 export function AppShell() {
   const [activeSessionId, setActiveSessionId] = useState<string | null>(null);
+  const { data: sessions = [] } = useQuery<SessionSummary[]>({
+    queryKey: ["sessions"], queryFn: listSessions, refetchInterval: 10_000,
+  });
   const composerRef = useRef<HTMLInputElement>(null);
 
   // The harness "holds the ball" whenever a session is live and no widget is
@@ -121,8 +126,10 @@ export function AppShell() {
         </div>
         <div className="flex-1 overflow-y-auto px-2 pb-4">
           <NavSessions
+            sessions={sessions}
             activeSessionId={activeSessionId}
-            onSessionSelect={setActiveSessionId}
+            onOpenPanel={async (id) => { await resumeSession(id); setActiveSessionId(id); }}
+            menuFor={() => null}
           />
         </div>
       </aside>