fix: clarify pooled output logic in SigLIP2
Author: sameerajashyam
Pull request: yes

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Clarified misleading comment in `modeling_siglip2.py` regarding pooled output token position.
 Updated the comment to reflect that the final token may be `<pad>` or `<eos>`, consistent with SigLIP2’s training (which does not use attention masks).
- Adjusted the `_no_split_modules` list to match Hugging Face's modular formatting guidelines.
- Verified consistency using `check_modular_conversion.py`.
 #39269


Comments:
Hey @sameerajashyam , looks like the changes were reverted after the modular conversion. You need to apply all changes in the `modular_siglip2.py` file and then run conversion to make CI happy :)

Thanks @zucchini-nlp! I’ve updated the `modular_siglip2.py` file with the intended changes and re-ran the modular converter script. The corresponding changes now appear in `modeling_siglip2.py` as expected. 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_39283). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

@sameerajashyam sorry, forgot to add this comment, I believe you meant to delete `# Assuming "sticky" EOS tokenization, last token is always EOS.` and update comment in Text Transformer, not Vision

**[For maintainers]** Suggested jobs to run (before merge)

run-slow: siglip2

Hi  @zucchini-nlp .I had  removed the outdated comment # Assuming "sticky" EOS tokenization, last token is always EOS. from both SigLIP and SigLIP2 text models (modeling_siglip.py and modeling_siglip2.py).

As mentioned in #39269, the model uses the final token embedding whether it’s [PAD] or [EOS], so the comment was no longer correct. I didn’t move it to the Text Transformer because it’s not needed anymore.

The PR got closed after force-pushing, feel free to re-open 

Hi @zucchini-nlp — thanks for the note on #39283.

I’ve since opened #39378 with all your feedback incorporated (and a new test case added). It’s clean, CI passed, and ready for review. 

Thanks again for your time and support!

https://github.com/huggingface/transformers/pull/39378