Use GitHub macOS 26 runners

[fkorotkov-oai]

What changed

• replace the Cirrus Labs macOS runner labels with GitHub-hosted macos-26
• collapse the Sequoia/Tahoe test matrix into one macOS 26 test job
• run release and snapshot jobs on the same GitHub-hosted image

Why

The release workflows should use the supported GitHub-hosted macOS 26 ARM64 image instead of Cirrus Labs runner images.

Installation

brew install openai/tools/softnet

Validation

• GOPATH=/Users/fkorotkov/.cache/codex-go GOMODCACHE=/Users/fkorotkov/.cache/codex-go/pkg/mod GOCACHE=/Users/fkorotkov/.cache/codex-go-build go run github.com/rhysd/actionlint/cmd/actionlint@v1.7.12 .github/workflows/*.yml
• git diff --check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Restore CI coverage for Sequoia

The release config still publishes the Homebrew formula as supported on macOS Sequoia via .goreleaser.yml's depends_on :macos => :sequoia, but this change removes the only Sequoia test leg and runs tests only on macOS 26. Changes that rely on Tahoe-only SDK/runtime behavior can now pass CI and be released to Sequoia users without detection; please keep a macos-15/Sequoia test leg or raise the published minimum.

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