[Bee] Incorrect reading order for Key Value regions

### Requested feature
For some content in the PDF document, it includes multiple columns or blocks with key and value regions, and the structure is not recognized as tables; the reading order should be key first, value second, one by one, but in the markdown results, they are mixed together.

For example:
file content

result:

There are several testing documents:

1. Summary section in [test_kvp_reading_order.pdf](https://github.com/user-attachments/files/29789718/test_kvp_reading_order.pdf), programmatic PDF
2. form section in [AB.FILES.038670001-02-PDF_A_MockUp-page-5.pdf](https://github.com/user-attachments/files/29789801/AB.FILES.038670001-02-PDF_A_MockUp-page-5.pdf), Form data, scanned PDF, but the section is not recognized as table.

Start by reproducing the markdown output with test_kvp_reading_order.pdf and AB.FILES.038670001-02-PDF_A_MockUp-page-5.pdf, comparing the reported key/value regions with their expected reading order. Trace the PDF-to-markdown reading-order entry point and add or update regression coverage so each key is followed by its corresponding value in both examples.

Written by the indexing model from the issue text.