codexbar: allow Intel Macs

[SSakutaro]

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removes the arm64 architecture requirement because the current CodexBar release ships universal macOS binaries.

Verified on Apple Silicon Mac:

• brew audit --cask --online codexbar
• brew audit --cask --strict --online codexbar
• brew style codexbar.rb

Verified on Intel Mac:

• HOMEBREW_NO_INSTALL_FROM_API=1 brew install --cask codexbar
• file /Applications/CodexBar.app/Contents/MacOS/CodexBar
• file /Applications/CodexBar.app/Contents/Helpers/CodexBarCLI
• brew uninstall --cask codexbar

Both CodexBar and CodexBarCLI are universal binaries containing x86_64 and arm64 slices

After making any changes to a cask, existing or new, verify:

• The submission is for a stable version or documented exception.
• brew audit --cask --online <cask> is error-free.
• brew style --fix <cask> reports no offenses.

Additionally, if adding a new cask:

• Named the cask according to the token reference.
• Checked the cask was not already refused (add your cask's name to the end of the search field).
• brew audit --cask --new <cask> worked successfully.
• HOMEBREW_NO_INSTALL_FROM_API=1 brew install --cask <cask> worked successfully.
• brew uninstall --cask <cask> worked successfully.

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• AI was used to generate or assist with generating this PR. Please specify below how you used AI to help you, and what steps you have taken to manually verify the changes, including zap stanza paths.

AI was used to help interpret Homebrew audit output and draft the PR description.
I manually verified the cask on Apple Silicon and Intel Macs using the commands listed above. No zap stanza paths were changed.

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