Simplify batch cleanup to explicit selection only

The age-based quick cleanup buttons overlapped poorly with the sidebar time groups and created ambiguity around what would be deleted. Keeping batch mode focused on all/selected sessions makes the destructive path easier to understand while preserving the existing confirmation and server deletion behavior.

Constraint: Desktop batch deletion should stay routed through the existing selected-session confirmation flow.
Rejected: Rename the age-based cleanup buttons | still leaves a low-value destructive shortcut in the primary batch panel.
Confidence: high
Scope-risk: narrow
Directive: Add future destructive cleanup shortcuts only when their target set is unambiguous in the current filtered session list.
Tested: cd desktop && bun run test src/components/layout/Sidebar.test.tsx
Tested: bun run check:desktop
Tested: git diff --check
Not-tested: Manual desktop click-through after removing the buttons.

desktop/src/components/layout/Sidebar.test.tsx

@@ -37,8 +37,6 @@ vi.mock('../../i18n', () => ({
       'sidebar.batchDeleteConfirm': 'Delete {count} sessions? This cannot be undone.',
       'sidebar.batchDeleteConfirmBody': 'The following sessions will be deleted:',
       'sidebar.batchDeleteMore': '...and {count} more',
-      'sidebar.batchClearOlderThan30': 'Clear >30d',
-      'sidebar.batchClearOlderThan7': 'Clear >7d',
       'sidebar.batchExit': 'Cancel batch mode',
       'sidebar.batchDeleteSucceeded': 'Deleted {count} sessions.',
       'sidebar.batchDeleteFailed': '{count} sessions could not be deleted.',

desktop/src/components/layout/Sidebar.tsx

@@ -186,12 +186,6 @@ export function Sidebar({ isMobile = false, onRequestClose }: SidebarProps) {
     }
   }, [deselectSessions, selectSessions, selectedSessionIds])
 
-  const selectOlderThan = useCallback((days: number) => {
-    const ids = getSessionsOlderThan(filteredSessions, days)
-    selectSessions(ids)
-    requestBatchDelete(ids)
-  }, [filteredSessions, requestBatchDelete, selectSessions])
-
   const handleStartRename = useCallback((id: string, currentTitle: string) => {
     setContextMenu(null)
     setRenamingId(id)
@@ -445,22 +439,6 @@ export function Sidebar({ isMobile = false, onRequestClose }: SidebarProps) {
                   >
                     {t('sidebar.batchDeleteSelected', { count: selectedCount })}
                   </button>
-                  <button
-                    type="button"
-                    onClick={() => selectOlderThan(7)}
-                    disabled={getSessionsOlderThan(filteredSessions, 7).length === 0}
-                    className="rounded-md border border-[var(--color-border)] px-2 py-1.5 text-xs font-medium text-[var(--color-text-secondary)] transition-colors hover:bg-[var(--color-surface-hover)] disabled:opacity-50"
-                  >
-                    {t('sidebar.batchClearOlderThan7')}
-                  </button>
-                  <button
-                    type="button"
-                    onClick={() => selectOlderThan(30)}
-                    disabled={getSessionsOlderThan(filteredSessions, 30).length === 0}
-                    className="rounded-md border border-[var(--color-border)] px-2 py-1.5 text-xs font-medium text-[var(--color-text-secondary)] transition-colors hover:bg-[var(--color-surface-hover)] disabled:opacity-50"
-                  >
-                    {t('sidebar.batchClearOlderThan30')}
-                  </button>
                 </div>
               </div>
             )}
@@ -719,13 +697,6 @@ function groupByTime(sessions: SessionListItem[]): Map<TimeGroup, SessionListIte
   return groups
 }
 
-function getSessionsOlderThan(sessions: SessionListItem[], days: number): string[] {
-  const threshold = Date.now() - days * 86400000
-  return sessions
-    .filter((session) => new Date(session.modifiedAt).getTime() < threshold)
-    .map((session) => session.id)
-}
-
 function NavItem({
   active,
   collapsed,

desktop/src/i18n/locales/en.ts

@@ -35,8 +35,6 @@ export const en = {
   'sidebar.batchDeleteConfirm': 'Delete {count} sessions? This cannot be undone.',
   'sidebar.batchDeleteConfirmBody': 'The following sessions will be deleted:',
   'sidebar.batchDeleteMore': '...and {count} more',
-  'sidebar.batchClearOlderThan30': 'Clear >30d',
-  'sidebar.batchClearOlderThan7': 'Clear >7d',
   'sidebar.batchExit': 'Cancel batch mode',
   'sidebar.batchDeleteSucceeded': 'Deleted {count} sessions.',
   'sidebar.batchDeleteFailed': '{count} sessions could not be deleted.',

desktop/src/i18n/locales/zh.ts

@@ -37,8 +37,6 @@ export const zh: Record<TranslationKey, string> = {
   'sidebar.batchDeleteConfirm': '确定要删除 {count} 个会话吗？此操作不可撤销。',
   'sidebar.batchDeleteConfirmBody': '以下会话将被删除：',
   'sidebar.batchDeleteMore': '...还有 {count} 条',
-  'sidebar.batchClearOlderThan30': '清空 30 天前',
-  'sidebar.batchClearOlderThan7': '清空 7 天前',
   'sidebar.batchExit': '退出批量管理',
   'sidebar.batchDeleteSucceeded': '已删除 {count} 个会话。',
   'sidebar.batchDeleteFailed': '有 {count} 个会话删除失败。',