#6094 - It is possible to create antisense even if it is not allowed (when base has extra bond out of r1-r3 to sugar)

[beyzaevcen]

How the feature works? / How did you fix the issue?

(Screenshots, videos, or GIFs, if applicable)

Summary

• When checking whether "Create Antisense Strand" should be disabled,
  the rnaBaseForSugar condition was missing the covalentBonds.length > 1
  check that already existed for directly selected RNABase monomers.
• This caused the option to remain enabled when a base (accessed via its sugar)
  had extra covalent bonds (e.g. nC6n5C bases connected via R2-R2 in HELM),
  allowing antisense creation to proceed incorrectly.
• Fix: added rnaBaseForSugar.covalentBonds.length > 1 to the disabled condition,
  making it consistent with the direct RNABase check.

Check list

• unit-tests written
• e2e-tests written
• documentation updated
• PR name follows the pattern #1234 – issue name
• branch name doesn't contain '#'
• PR is linked with the issue
• base branch (master or release/xx) is correct
• task status changed to "Code review"
• reviewers are notified about the pull request