CI: GitHub retires the macos-14 runners on 2026-11-02 #219

GitHub retires its macOS 14 runner images on 2026-11-02 (actions/runner-images#13518). Until then, scheduled brownouts already fail every macOS 14 job between 14:00 and 00:00 UTC. #218 failed this way on 2026-10-31.

Two workflows use the image:

• build.yml builds and tests on macos-14. Its job, Build on macos-14, is a required check of main, so from 2026-11-02 no pull request can be merged.
• release-binaries.yml builds the macOS disk image on macos-14, so no release could ship one.

Change

• Build and test on macos-15.
• Build the disk image on macos-15, with a deployment target of 15.0.
  • The image ships Homebrew libraries built for the runner's macOS.
  • package-macos.sh refuses an image whose files need a newer macOS than the target.
  • So the image will need macOS 15 or newer.
• Say so in the README, the CHANGELOG and the reproducibility protocol.
• In the protect-main ruleset, replace the required check Build on macos-14 with Build on macos-15.

Acceptance

• Build on macos-15 and Build macOS binary (arm64) pass. The second packages the disk image and verifies it.
• main requires Build on macos-15 instead of Build on macos-14.