Sparse two-column text and right-aligned tags are merged horizontally across wide gutters

### Summary
On pages with side-by-side columns or right-aligned header tags, text items sharing the same vertical line are incorrectly merged horizontally across wide gutters, interleaving separate columns line-by-line and appending header tags directly into titles.

### Reproduction
Tested with sample PDF: [en-22-mixed-layout.pdf](https://github.com/fuchengwang/pdf-samples/blob/main/en-22-mixed-layout.pdf) ([Direct download](https://raw.githubusercontent.com/fuchengwang/pdf-samples/main/en-22-mixed-layout.pdf)).

**Actual Output:**
```markdown
# Mixed layout report EN-22

Left column: record source type, page count, and Right column: inspect tables, images, links, and reading checksum. order.
```

**Expected Output:**
```markdown
# Mixed layout report

EN-22

Left column: record source type, page count, and checksum.

Right column: inspect tables, images, links, and reading order.
```

### Sample File
- [en-22-mixed-layout.pdf (GitHub viewer)](https://github.com/fuchengwang/pdf-samples/blob/main/en-22-mixed-layout.pdf)
- [en-22-mixed-layout.pdf (Raw download)](https://raw.githubusercontent.com/fuchengwang/pdf-samples/main/en-22-mixed-layout.pdf)

Start by reproducing the issue with en-22-mixed-layout.pdf and trace the PDF text-extraction or layout-ordering entry point that produces the shown Markdown. Done means the two columns and right-aligned tag remain separate as in the expected output, with regression coverage for this sample.

Written by the indexing model from the issue text.