refactor(sidebar): put the update check first, group the folder entries (#999)

The folder context menu now reads: the content action (check for updates)
on top, then the folder operations as one group (new subfolder, rename),
then the destructive entry behind its own divider.

Gating the three folder entries per page could leave the menu with
dangling separators — the recipes sidebar hides all of them and keeps
only the update check, which already rendered one stray divider before
this change and would have rendered two after it. Add
_updateContextMenuSeparators: a divider survives only when a visible
entry sits on both sides, and a run of consecutive ones collapses to a
single line. The three per-item display toggles fold into one loop.

The template order is guarded by a regression test that parses
templates/components/context_menu.html, plus behaviour tests for the
divider collapsing.

tests/frontend/components/sidebarManager.folderManagement.test.js

@@ -846,3 +846,75 @@ describe('SidebarManager folder rename', () => {
   });
 });
 
+describe('SidebarManager folder context menu layout', () => {
+  // Mirrors templates/components/context_menu.html: the update check on top,
+  // the folder operations as one group, delete last behind its own divider.
+  const MENU_HTML = `
+    <div id="sidebarFolderContextMenu" class="context-menu">
+      <div class="context-menu-item" data-action="check-folder-updates"></div>
+      <div class="context-menu-separator"></div>
+      <div class="context-menu-item" data-action="create-subfolder"></div>
+      <div class="context-menu-item" data-action="rename-folder"></div>
+      <div class="context-menu-separator"></div>
+      <div class="context-menu-item delete-item" data-action="delete-folder"></div>
+    </div>`;
+
+  const separators = () => [...document.querySelectorAll('#sidebarFolderContextMenu .context-menu-separator')];
+  const item = (action) => document.querySelector(`#sidebarFolderContextMenu [data-action="${action}"]`);
+  const visible = (el) => el.style.display !== 'none';
+
+  beforeEach(() => {
+    localStorage.clear();
+    document.body.innerHTML = MENU_HTML;
+    state.global.settings = {};
+    vi.clearAllMocks();
+  });
+
+  it('keeps both dividers on a library page', () => {
+    const manager = createManager(createApiClient());
+
+    manager._showFolderContextMenu(10, 10, 'empty');
+
+    expect(separators().map(visible)).toEqual([true, true]);
+    expect(visible(item('create-subfolder'))).toBe(true);
+    expect(visible(item('rename-folder'))).toBe(true);
+    expect(visible(item('delete-folder'))).toBe(true);
+
+    manager._closeFolderContextMenu();
+  });
+
+  it('collapses both dividers when the page has no folder management', () => {
+    const apiClient = createApiClient();
+    apiClient.apiConfig.config.supportsFolderManagement = false;
+    const manager = createManager(apiClient);
+
+    manager._showFolderContextMenu(10, 10, 'empty');
+
+    expect(visible(item('check-folder-updates'))).toBe(true);
+    expect(visible(item('create-subfolder'))).toBe(false);
+    expect(visible(item('rename-folder'))).toBe(false);
+    expect(visible(item('delete-folder'))).toBe(false);
+    // Nothing left to divide: the update check stands alone
+    expect(separators().map(visible)).toEqual([false, false]);
+
+    manager._closeFolderContextMenu();
+  });
+
+  it('drops leading, trailing and doubled separators', () => {
+    document.body.innerHTML = `
+      <div id="sidebarFolderContextMenu" class="context-menu">
+        <div class="context-menu-separator"></div>
+        <div class="context-menu-item" data-action="a"></div>
+        <div class="context-menu-separator"></div>
+        <div class="context-menu-separator"></div>
+        <div class="context-menu-item" data-action="b"></div>
+        <div class="context-menu-separator"></div>
+      </div>`;
+    const manager = createManager(createApiClient());
+
+    manager._updateContextMenuSeparators(document.getElementById('sidebarFolderContextMenu'));
+
+    expect(separators().map(visible)).toEqual([false, true, false, false]);
+  });
+});
+