diagnostic: cap OCLP tier when macOS is outdated

[p-linnane]

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Claude Code with local review and verification.

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Fixes https://github.com/orgs/Homebrew/discussions/6835.

[Copilot]

Pull request overview

Adjusts the macOS diagnostics messaging for OpenCore Legacy Patcher (OCLP) so that when the host macOS is an outdated release, the reported support tier is capped at Tier 3 (even on otherwise “modern” Intel CPUs). This aligns OCLP guidance with the existing “outdated macOS” support-tier policy.

Changes:

• Update check_for_opencore to return Tier 3 when OS::Mac.version.outdated_release? is true.
• Add RSpec coverage for check_for_opencore tier selection across (modern CPU / old CPU) and (supported macOS / outdated macOS) scenarios.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/extend/os/mac/diagnostic.rb	Caps OCLP support tier at Tier 3 when running an outdated macOS release.
Library/Homebrew/test/os/mac/diagnostic_spec.rb	Adds unit tests validating Tier 2 vs Tier 3 selection for OCLP based on CPU features and outdated macOS state.

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[MikeMcQuaid]

Makes sense thanks!