[turinglambdaai]

Why

Windows selection parity requires actual useful bulk actions, not merely highlighting rows. This adds a small contextual action bar for two or more selected tasks in the normal and global-search task list.

Changes

• Shared contextual toolbar appears for 2+ selected task IDs and provides Complete Selected and Move to List. All labels are localized in zh/en.
• Selected task IDs are snapshotted synchronously before dispatching async backend mutations, so changed-event snapshot refreshes cannot redirect operations.
• Completion targets only currently incomplete tasks; move skips items already in the destination. Both use existing typed backend API and error reporting, preserving all other fields.
• Add a packaged Windows UI Automation regression: create two tasks in 生活, select both through SelectionItemPattern, invoke batch complete, then assert that both disappear from the pending list.
• Document intentionally remaining parity gaps.

Dependencies

Stacked on #41 → #39 → #36 → #35 → #32. Merge bottom-up, review reduced diff, then rerun integrated CI and product acceptance.

QA before merge

• Windows native build and packaged Product Acceptance pass
• Ctrl/Shift selection and focus behave naturally at 100/150% DPI
• Batch-complete mixed completed/incomplete selection changes only pending rows
• Batch move across 工作/生活 preserves text, notes, due dates and completion
• From search results, batch operations target the actual owning tasks, not the active sidebar list
• Check no duplicate actions under changed-event reload

Not included: bulk due-date scheduling, bulk delete with undo, native inline detail editing. These are still tracked for release parity; do not publish solely based on this PR passing.