feat: US-004 — App shell layout and sidebar navigation

- Add electron-store@8 for sidebar collapse state persistence via settings tRPC router
- Add @fontsource/geist for self-hosted Geist font (remove Google Fonts CDN)
- Add right-edge vertical 'keep scrolling for AI' label with chevron-down in all views
- Wire AppShell collapse toggle to settings.setSidebarCollapsed tRPC mutation
- Fix ESLint config with eslint-import-resolver-typescript to resolve @/* path aliases

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

src/renderer/components/layout/AppShell.tsx

@@ -6,8 +6,10 @@ import {
   ClipboardCheck,
   FolderKanban,
   PanelLeft,
+  ChevronDown,
 } from 'lucide-react';
 import { cn } from '@/lib/utils';
+import { trpc } from '@/lib/trpc';
 
 const NAV_ITEMS = [
   { to: '/', icon: House, label: 'Home' },
@@ -21,10 +23,25 @@ interface AppShellProps {
 }
 
 export function AppShell({ children }: AppShellProps) {
-  const [collapsed, setCollapsed] = useState(false);
+  const collapsedQuery = trpc.settings.getSidebarCollapsed.useQuery(undefined, {
+    staleTime: Infinity,
+  });
+  const setSidebarCollapsedMutation = trpc.settings.setSidebarCollapsed.useMutation();
+
+  // localCollapsed tracks user toggles after load; null means "use server value"
+  const [localCollapsed, setLocalCollapsed] = useState<boolean | null>(null);
+
   const routerState = useRouterState();
   const currentPath = routerState.location.pathname;
 
+  const collapsed = localCollapsed !== null ? localCollapsed : (collapsedQuery.data ?? false);
+
+  const handleToggle = () => {
+    const next = !collapsed;
+    setLocalCollapsed(next);
+    setSidebarCollapsedMutation.mutate({ collapsed: next });
+  };
+
   return (
     <div className="flex h-screen w-screen overflow-hidden bg-background">
       {/* Sidebar */}
@@ -90,7 +107,7 @@ export function AppShell({ children }: AppShellProps) {
         {/* Collapse toggle */}
         <div className="px-2 pb-3 shrink-0">
           <button
-            onClick={() => setCollapsed((c) => !c)}
+            onClick={handleToggle}
             className={cn(
               'flex items-center gap-2 h-8 px-3 rounded-md text-sm text-sidebar-foreground w-full',
               'hover:bg-sidebar-accent transition-colors',
@@ -107,6 +124,19 @@ export function AppShell({ children }: AppShellProps) {
       {/* Main content */}
       <main className="flex-1 min-w-0 overflow-hidden relative">
         {children}
+
+        {/* Right-edge vertical 'keep scrolling for AI' affordance (non-interactive) */}
+        <div className="absolute right-0 top-0 bottom-0 flex items-end justify-center pb-8 pointer-events-none select-none">
+          <div className="flex flex-col items-center gap-1.5 pr-2">
+            <span
+              className="text-[9px] text-muted-foreground/30 tracking-widest uppercase font-medium"
+              style={{ writingMode: 'vertical-rl', transform: 'rotate(180deg)' }}
+            >
+              keep scrolling for AI
+            </span>
+            <ChevronDown size={10} className="text-muted-foreground/30" />
+          </div>
+        </div>
       </main>
     </div>
   );