ci(.github/workflows): pin macos-15 runner to avoid macOS 26 SDK link failure (#94)

Author: kylecarbs

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest]
+        os: [ubuntu-latest, macos-15]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6