fix: ensure sentence_transformers_similarity score is a float to not np.float

[abdokaseb]

Related Issues

• fixes SentenceTransformersSimilarityRanker returns Documents with numpy score #9664

Proposed Changes:

The SentenceTransformersSimilarityRanker CrossEncoder model was returning score as a numpy.float32 without casting to float, which can cause JSON serialization issues in downstream integrations.

Explicitly cast the score to a standard Python float before assigning it to Document.score.

How did you test it?

Added a unit test to verify that Document.score is always a Python float.
Ran all existing unit tests with hatch run test:unit to ensure no regressions.

Notes for the reviewer

The change is minimal but important for serialization compatibility.

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[CLAassistant]

All committers have signed the CLA.

[coveralls]

Pull Request Test Coverage Report for Build 16703692448

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 91.885%

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Files with Coverage Reduction	New Missed Lines	%
core/pipeline/async_pipeline.py	3	66.88%

Totals
Change from base Build 16654540600:	-0.02%
Covered Lines:	12794
Relevant Lines:	13924

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💛 - Coveralls

[anakin87]

Thanks for this PR!

Overall, it's good.
I left some minor comments to address...

[anakin87]

Looks good.
Thanks again!