rubocops/move_to_extend_os: audit OS checks in extend/os

[ZhongRuoyu]

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Extend the Homebrew/MoveToExtendOS cop to identify incorrect or redundant OS.mac? and OS.linux? checks in extend/os/{mac,linux}.

Originally proposed in #20738 (comment).

[Copilot]

Pull request overview

Extends the existing Homebrew/MoveToExtendOS RuboCop cop so it can also audit extend/os/mac and extend/os/linux for incorrect/redundant OS.mac?/OS.linux? checks, aligning with Homebrew’s OS-specific extension layout under extend/os.

Changes:

• Update Homebrew/MoveToExtendOS to emit targeted offenses for OS.mac?/OS.linux? calls inside extend/os/mac and extend/os/linux.
• Adjust RuboCop configuration so the cop runs on extend/** (while still excluding tests/requirements).
• Add RSpec coverage and update the Sorbet RBI for the new node matchers.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/rubocops/move_to_extend_os.rb	Implements path-aware offenses for extend/os/mac and extend/os/linux, while preserving the existing “move to extend/os” behavior elsewhere.
Library/Homebrew/.rubocop.yml	Enables the cop for extend/** by removing extend from the exclusion glob.
Library/Homebrew/test/rubocops/move_to_extend_os_spec.rb	Adds tests verifying offenses are raised for redundant/incorrect OS checks under extend/os/mac and extend/os/linux.
Library/Homebrew/sorbet/rbi/dsl/rubo_cop/cop/homebrew/move_to_extend_os.rbi	Updates the RBI to reflect the new os_mac? / os_linux? node matcher methods.

Files not reviewed (1)

• Library/Homebrew/sorbet/rbi/dsl/rubo_cop/cop/homebrew/move_to_extend_os.rbi: Language not supported

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[MikeMcQuaid]

Good catch, thanks!