fix: correct default sidebar state initialization and adjust sidebar width

src/renderer/components/layout/AppShell.tsx

@@ -45,8 +45,9 @@ export function AppShell({ children }: AppShellProps) {
   const currentPath = routerState.location.pathname;
 
   // Controlled open state (spec: "Controlled Sidebar" pattern)
+  // Default to collapsed (false) until the persisted preference loads
   const [open, setOpen] = useState(() =>
-    collapsedQuery.data === undefined ? true : !collapsedQuery.data
+    collapsedQuery.data === undefined ? false : !collapsedQuery.data
   );
 
   const handleOpenChange = (value: boolean) => {

src/renderer/components/ui/sidebar.tsx

@@ -27,7 +27,7 @@ import {
 
 const SIDEBAR_COOKIE_NAME = "sidebar_state"
 const SIDEBAR_COOKIE_MAX_AGE = 60 * 60 * 24 * 7
-const SIDEBAR_WIDTH = "16rem"
+const SIDEBAR_WIDTH = "12rem"
 const SIDEBAR_WIDTH_MOBILE = "18rem"
 const SIDEBAR_WIDTH_ICON = "3rem"
 const SIDEBAR_KEYBOARD_SHORTCUT = "b"