docs/Gemfile: add irb to silence Ruby 4.0 warning

[p-linnane]

YARD's yard/parser/ruby/legacy/irb/slex.rb requires irb/notifier, which triggers a warning under Ruby 4.0 since irb is no longer a default gem:

yard-0.9.43/lib/yard/parser/ruby/legacy/irb/slex.rb:14: warning: irb/notifier is found in irb, which is not part of the default gems since Ruby 4.0.0.
You can add irb to your Gemfile or gemspec to fix this error.

Upstream lsegal/yard#1663 only wraps the require in begin/rescue LoadError, which doesn't help here since irb is in fact installed — Ruby's bundled-gem hook fires the warning before the rescue is relevant. (The actual fix, lsegal/yard#1649, was closed in favor of #1663.)

Declaring irb as an explicit dependency satisfies Ruby's bundled-gem activation check and silences the warning.

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Diagnosed the warning, traced it through bundled_gems.rb to confirm Ruby's hook (not yard itself) is what fires it, and drafted the change with Claude. Verified locally:

$ bundle exec rake yard 2>&1 | grep irb
$ # (no output — warning gone)

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[Copilot]

Pull request overview

This PR makes irb an explicit dependency for the docs bundle to avoid Ruby 4.0 bundled-gem warnings when YARD loads irb/notifier.

Changes:

• Adds irb to docs/Gemfile.
• Updates docs/Gemfile.lock with irb and its transitive dependencies.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 1 comment.

File	Description
docs/Gemfile	Declares irb as a docs dependency.
docs/Gemfile.lock	Locks irb and related transitive gems for the docs bundle.

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[MikeMcQuaid]

Thanks!