Fix typos in documentation and README files

[kojix2]

Fix typos

[Copilot]

Pull Request Overview

This PR fixes multiple spelling errors in documentation and code comments across the IRuby project, improving the overall readability and professionalism of the codebase.

• Corrects "old-stle" to "old-style" in session description
• Fixes "interferring" to "interfering" in README documentation
• Corrects "deault" to "default" in input documentation
• Fixes "accross" to "across" in CHANGES.md

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
lib/iruby/session/cztop.rb	Fixes typo in session description comment
lib/iruby/input/README.md	Corrects spelling errors in documentation text
lib/iruby/input/README.ipynb	Same spelling corrections as README.md for Jupyter notebook format
CHANGES.md	Fixes typo in changelog entry

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