feat: improve extraction from fillable fields

[PeterStaar-IBM]

original screenshot:

rendered image (after parse):

fillable_form.pdf

using

./render.exe -i ../tests/data/regression/fillable_form.pdf -l info --do-sanitization=false --create-word-cells=false --create-line-cells=false -r blend2d

adressing: docling-project/docling#2899

[mergify]

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

[github-actions]

✅ DCO Check Passed

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