adapt arxiv search to new response format

[20001LastOrder]

Description

It seems recently the arXiv search has been changed to return an extra title element for the search result itself, which causes one existing test to fail. This fix aligns the number of title elements and summary elements to ensure consistency.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Maintenance
• New release

Checklists

To speed up the review process, please follow these checklists:

Development

• The Pull Request is small and focused on one topic
• Lint rules pass locally (make format && make lint)
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development (make test)
• The changes generate no new warnings (or explain any new warnings and why they're ok)
• Commit messages are detailed
• Changed code is self-explanatory and/or I added comments
• I updated the documentation (docstrings, /docs)
  See the testing guidelines for help on tests, especially those involving web services.

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached.
• I have performed a self-review of my code
• Issue from task tracker has a link to this pull request

💔 Thank you for submitting a pull request!

[amirfz]

Closing as superseded: this patches the old whole-document regex parser (re.findall over the entire XML feed, then slicing titles to align with summaries). That code no longer exists — b5c283e (part of #509, merged) rewrote arXiv parsing to work per-<entry> block instead, which can't misalign title/summary/id fields in the first place (it skips any entry missing a field rather than relying on count-alignment). Current main already handles the case this PR was fixing, more robustly.