fix: serialization into DCLX on splitted text across pages

[PeterStaar-IBM]

we fix this,

into

Summary

• Preserve page-local pictures and captions when a preceding paragraph spans multiple pages.
• Regroup threaded fragments by provenance page before emitting <page_break/>.
• Add dclx output support to docling-serialize.
• Package page images under pages/ and picture assets under assets/.
• Require --output for binary DCLX output.

Usage

docling-serialize document.json --to dclx --output document.dclx

[github-actions]

✅ DCO Check Passed

Thanks @PeterStaar-IBM, all your commits are properly signed off. 🎉

[mergify]

Merge Protections

🟢 All 2 merge protections satisfied — ready to merge.

Show 2 satisfied protections

🟢 Enforce conventional commit

Make sure that we follow https://www.conventionalcommits.org/en/v1.0.0/

• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?(!)?:

🟢 Require two reviewer for test updates

When test data is updated, we require two reviewers

• #approved-reviews-by >= 2

[dolfim-ibm]

lgtm

[codecov]

Codecov Report

❌ Patch coverage is 83.87097% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
docling_core/transforms/serializer/doclang.py	83.01%	9 Missing ⚠️
docling_core/cli/serialize.py	88.88%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!