feat(ui): make desktop sidebar collapsible

Add a header toggle and a panel close button so the desktop file
sidebar collapses with a width transition, mirroring the journal
panel.

- split onClose (close button) from onNavigate (file selection) so
  clicking a file no longer collapses the sidebar on desktop
- give the aside h-full so the file tree and outline keep bounded
  scroll regions inside the new wrapper
- swap the aside shadow for a gray right border to match the journal

src/components/Sidebar.tsx

@@ -18,7 +18,7 @@ interface SidebarContentProps {
   pathHeadings: Record<string, TocNode[]>;
   currentPath: string;
   onClose: () => void;
-  isDesktop?: boolean;
+  onNavigate?: () => void;
   onDataSourceOpen?: () => void;
 }
 
@@ -60,15 +60,13 @@ const SidebarContent: Component<SidebarContentProps> = (props) => {
             >
               <TbOutlineFolderOpen class="inline-block align-[-0.125em]" />
             </button>
-            <Show when={!props.isDesktop}>
-              <button
-                onClick={props.onClose}
-                class="text-gray-500 hover:text-gray-700"
-                title="关闭"
-              >
-                <TbOutlineX class="inline-block align-[-0.125em]" />
-              </button>
-            </Show>
+            <button
+              onClick={props.onClose}
+              class="text-gray-500 hover:text-gray-700"
+              title="关闭"
+            >
+              <TbOutlineX class="inline-block align-[-0.125em]" />
+            </button>
           </div>
         </div>
       </div>
@@ -84,7 +82,7 @@ const SidebarContent: Component<SidebarContentProps> = (props) => {
             currentPath={props.currentPath}
             pathHeadings={props.pathHeadings}
             depth={0}
-            onClose={props.onClose}
+            onClose={() => props.onNavigate?.()}
             isHidden={isFileHidden}
           />
         ))}
@@ -151,6 +149,7 @@ export const MobileSidebar: Component<SidebarProps> = (props) => {
           pathHeadings={pathHeadings()}
           currentPath={location.pathname}
           onClose={props.onClose}
+          onNavigate={props.onClose}
           onDataSourceOpen={props.onDataSourceOpen}
         />
       </aside>
@@ -164,6 +163,7 @@ export const MobileSidebar: Component<SidebarProps> = (props) => {
 export const DesktopSidebar: Component<{
   fileTree?: FileNode[];
   pathHeadings?: Record<string, TocNode[]>;
+  onClose: () => void;
   onDataSourceOpen?: () => void;
 }> = (props) => {
   const location = useLocation();
@@ -183,13 +183,12 @@ export const DesktopSidebar: Component<{
   });
 
   return (
-    <aside class="hidden md:flex flex-col w-64 shrink-0 bg-white shadow-lg overflow-hidden">
+    <aside class="hidden md:flex flex-col h-full w-64 shrink-0 bg-white border-r border-gray-200 overflow-hidden">
       <SidebarContent
         fileTree={fileTree()}
         pathHeadings={pathHeadings()}
         currentPath={location.pathname}
-        onClose={() => {}}
-        isDesktop
+        onClose={props.onClose}
         onDataSourceOpen={props.onDataSourceOpen}
       />
     </aside>