fix(ci): restore Intel macOS build in the release matrix

The Blacksmith migration left only arm64 macOS runners, so releases
stopped producing hack-<v>-darwin-x86_64.tar.gz and the homebrew tap
render fails on the missing asset (first seen on v3.1.0; v3.0.0 was
cut pre-migration). macos-15-intel restores the x86_64 tarball.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: roodboi

.github/workflows/release.yml

@@ -69,6 +69,9 @@ jobs:
           - os: blacksmith-6vcpu-macos-15
             upload_install: false
             skip_tests: true
+          - os: macos-15-intel
+            upload_install: false
+            skip_tests: true
     steps:
       - name: Checkout
         uses: actions/checkout@v4