feat(frontend): add database management surface

frontend/src/shell/SessionDocumentsPanel.tsx

@@ -13,6 +13,7 @@ interface Props {
   onClose: () => void;
   onResume: (id: string) => void;
   desktopSplit?: boolean;
+  hidden?: boolean;
 }
 
 function statusLabel(s: SessionSummary): string {
@@ -150,7 +151,7 @@ function decisionChipClass(type: string): string {
   return "bg-[oklch(var(--primary)/0.1)] text-primary";
 }
 
-export function SessionDocumentsPanel({ session, onClose, onResume, desktopSplit = false }: Props) {
+export function SessionDocumentsPanel({ session, onClose, onResume, desktopSplit = false, hidden = false }: Props) {
   const { data: docs = [], isLoading } = useQuery<SessionDocument[]>({
     queryKey: ["session-documents", session.id],
     queryFn: () => getSessionDocuments(session.id),
@@ -160,6 +161,8 @@ export function SessionDocumentsPanel({ session, onClose, onResume, desktopSplit
   return (
     <aside
       aria-label="Session summary"
+      aria-hidden={hidden || undefined}
+      hidden={hidden}
       className={[
         "flex shrink-0 flex-col border-r border-border bg-sidebar",
         desktopSplit