[GH-7317] Update Rubyzen gem name

[Stelios Frantzeskakis (steliosfran)]

What changed and why

Checklist

• Tests are added or updated for the changes
• bundle exec rspec spec/ passes locally

[GH-7317] Update Rubyzen gem name

[Copilot]

Pull request overview

This PR renames the packaged gem from rubyzen to rubyzen-lint while preserving the existing require 'rubyzen' entrypoint, adding shim files and updating packaging metadata so Bundler/RubyGems load the renamed gem cleanly.

Changes:

• Renamed the gemspec spec.name to rubyzen-lint and updated packaged file list accordingly.
• Updated README installation instructions to use gem 'rubyzen-lint'.
• Added require shims (lib/rubyzen-lint.rb, lib/rubyzen/lint.rb) and updated Zeitwerk ignores to prevent loader mapping errors.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
rubyzen-lint.gemspec	Renames gem to rubyzen-lint and updates packaged gemspec filename in spec.files.
README.md	Updates Gemfile snippet to install rubyzen-lint.
lib/rubyzen/lint.rb	Adds compatibility require shim for require 'rubyzen/lint'.
lib/rubyzen.rb	Ignores new shim files in Zeitwerk to avoid constant/file mapping conflicts.
lib/rubyzen-lint.rb	Adds gem-name entrypoint that forwards to rubyzen.
Gemfile.lock	Updates lockfile to reflect the new local gem name rubyzen-lint.