[Bee] docling parse generates text as each character separated

### Bug
With `DoclingParseV4DocumentBackend`, the plain text or Markdown output renders programmatic PDF page as "T i t l e C a s e W o r k e r s ..." instead of "Title Case Workers ...". However, `PyPdfiumDocumentBackend` is correct.

### Steps to reproduce
1. set standard pdf pipeline with `DoclingParseV4DocumentBackend`
2. do document convert
3. export md or plain text to check the output

Test file: because it is a customer file, please downlow it from https://github.ibm.com/ai-foundation/watson-doc-understanding-issue-tracker/issues/4015#issuecomment-233084821

### Docling version
docling-parse from 7.0.0 -> 7.11.0

### Python version
3.12

Start by obtaining the customer PDF from the linked issue and reproducing the standard pipeline with DoclingParseV4DocumentBackend, exporting Markdown or plain text. Compare its character spacing with PyPdfiumDocumentBackend; done means the Docling Parse output preserves normal word spacing for the supplied document.

Written by the indexing model from the issue text.