[Bug Report] element2 datepicker type=week or type=date,picker-options->firstDayOfWeek = 2, bug.

### Element UI version
2.15.14

### OS/Browsers version
win11

### Vue version
2.6.7

### Reproduction Link
https://codepen.io/luo19/pen/MYyxvVm

### Steps to reproduce
本地时间为20251212，el-datepicker 设置type="week", :picker-options="{firstDayOfWeek: 2}"，当el-date-picker__header上日期为2025-12月时，选择50周，pannel关闭后再打开选择的是下一周。当el-date-picker__header上日期为2025-11月时都是OK的，firstDayOfWeek=4时没有这个问题，不配置firstDayOfWeek也是正常的，具体可以看操作步骤视频。
把type=week 改成type=date也有这个问题。

The local time is 20251212. When using `el-datepicker` with `type="week"` and `:picker-options="{firstDayOfWeek: 2}"`, selecting week 50 when the date displayed in `el-date-picker__header` is December 2025 results in the next week being selected upon reopening the panel. However, when the date in `el-date-picker__header` is November 2025, everything functions correctly. The issue does not occur when `firstDayOfWeek=4`, nor when `firstDayOfWeek` is not configured. For detailed steps, refer to the instructional video.
Changing type=week to type=date also presents this issue.

https://www.bilibili.com/video/BV1GimEBtEaS/

### What is Expected?
当el-date-picker__header上日期为2025-12月时与el-date-picker__header上日期为2025-11月时操作后选择的week一致

When the date on the `el-date-picker__header` is December 2025, the selected week remains consistent with the selection when the date is November 2025

### What is actually happening?
当el-date-picker__header上日期为2025-12月时与el-date-picker__header上日期为2025-11月时操作后选择的week不一致，例如el-date-picker__header上日期为2025-12的选中50周，会变成51周，计算有问题。

When the date on el-date-picker_header is between December 2025 and November 2025, the week selected after the operation is inconsistent. For example, if 50 weeks are selected for the date on el-date-picker_header between December 2025 and November 2025, it will become 51 weeks, which is a calculation problem.