fix(docx): split multiple OMML equations into separate formula items

[giulio-leone]

Summary

When a DOCX paragraph contains multiple sibling <m:oMath> elements (e.g. two separate equations on one line), the converter concatenated them into a single LaTeX string because element.iter() walks all descendants depth-first, mixing children from different oMath nodes.

Root Cause

_handle_equations_in_text() used element.iter() (deep iteration) to collect both text runs and math elements. With multiple sibling <m:oMath> elements:

<w:p>
</w:p>

iter() would visit the children of the first oMath AND the second oMath and its children — all interleaved. The result was a single concatenated equation string.

Fix

1. Direct-children-first iteration: Check for oMath elements at the direct child level. If found, iterate direct children only, converting each oMath sibling independently. Falls back to the original deep iteration when oMath elements are nested inside wrapper elements like oMathPara.

2. Split standalone multi-equation paragraphs: When a paragraph contains only equations (no surrounding text) and has more than one equation, each is now emitted as a separate FORMULA document item instead of merging into one.

Before / After

Before: A paragraph with equations E = mc^2 and F = ma produced:

FORMULA: "E = mc^2 F = ma"

After: Two separate items:

FORMULA: "E = mc^2"
FORMULA: "F = ma"

Closes #3121

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[dolfim-ibm]

@giulio-leone can you please add the document attached to the linked issue as a test?

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✅ All modified and coverable lines are covered by tests.

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[giulio-leone]

@dolfim-ibm Done — added tests/data/docx/omml_multi_equation_paragraph.docx (a minimal DOCX with two sibling oMath elements separated by a text run) along with matching groundtruth files (md, json, itxt).

The test document validates that the fix correctly splits the equations into two separate FormulaItem entries instead of concatenating them.

[giulio-leone]

Pushed a follow-up CI fix. The new fixture itself was fine, but I had generated the .itxt snapshot with the wrong exporter. I regenerated omml_multi_equation_paragraph.docx.itxt using the same _export_to_indented_text(max_text_len=70, explicit_tables=False) path that test_backend_msword.py actually validates.

[M-Hassan-Raza]

Thanks for putting this together. The fix direction looks right, but I don’t think the new fixture is covering the exact failing shape from #3121.

The issue is specificlly about a single paragraph made up only of sibling m:oMath elements, with no text runs between them. On current main, that case still collapses into one display block and the equation ordder gets scrambled. The fixture added here looks more like formula-text-formula inline content, which current main already seems to handle correctly.

I’d suggest adding a regression fixture that matches the issue attachment more directly: one paragraph, multiple sibling m:oMath nodes, no intervening text. That would make it much clearer that this PR is locking down the reported bug and not a nearby case.

PSA: I am new to this coedbase so I could be wrong, in which case please feel free to discard this comment.

[giulio-leone]

Hi @dolfim-ibm, @M-Hassan-Raza — thanks for the detailed feedback! I'll add the test document from the linked issue and update the fixture to properly cover the exact failing shape (sibling m:oMath elements with no text runs between them). Will push an update shortly.

[giulio-leone]

Thanks @dolfim-ibm @M-Hassan-Raza for the feedback!

I've now:

1. Replaced the test document with the real Word file from issue Multiple OMML equations in one paragraph concatenated into a single display block #3121 (the ~37 KB document from @smroels containing three sibling <m:oMath> elements in one paragraph)
2. Regenerated all groundtruth files for the new document

The conversion correctly produces three separate equation blocks:

$$a=b$$
$$c=d$$
$$e=f$$

Ready for re-review!

[giulio-leone]

Hi team! 👋 The mergify bot indicates this PR requires two reviewers for test updates. Could a second reviewer (@PeterStaar-IBM, @cau-git, or @ceberam) take a look when convenient? The DCO check is now passing and all groundtruth files have been regenerated. Thank you!

[cau-git]

@giulio-leone Thanks for taking care of the feedback. Could you please re-run your pre-commit toolchain to ensure the tests pass?

uv run pre-commit install # only once in your dev setup
uv run pre-commit run --all-files # you can make a new commit and it will do this for you automatically.

[giulio-leone]

I reran the requested formatting/tooling pass and pushed the result.

Local verification

• uv run --python 3.12 pre-commit run --all-files ✅
• uv run --python 3.12 pytest tests/test_backend_msword.py -q ✅ (17 passed, 1 xfailed, 1 xpassed)

Real DOCX proof on the issue fixture

I also re-ran the actual conversion on tests/data/docx/omml_multi_equation_paragraph.docx and compared origin/main against this PR branch.

• origin/main produced 1 concatenated formula item: c=de=fa=b
• this PR branch produced 3 separate formula items: a=b, c=d, e=f

The markdown export matches that behavior as well:

• origin/main => one $$c=de=fa=b$$ block
• this PR => three separate formula blocks

The only new commit on the branch is the formatter rerun requested by CI / review:

• 7f3faed style(docx): rerun ruff formatter for msword backend