fix(ci): use macos-15-intel runner (macos-13 retired)

- Updated from deprecated macos-13 to macos-15-intel
- See: actions/runner-images#13046

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Oliver Baer

.github/workflows/release.yaml

@@ -65,10 +65,10 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          # Use macos-13 (Intel) for reliable cross-compilation to both architectures
-          - platform: macos-13
+          # Use macos-15-intel for reliable cross-compilation to both architectures
+          - platform: macos-15-intel
             args: --target aarch64-apple-darwin
-          - platform: macos-13
+          - platform: macos-15-intel
             args: --target x86_64-apple-darwin
           - platform: ubuntu-22.04
             args: ""
@@ -93,7 +93,7 @@ jobs:
       - name: Install Rust stable
         uses: dtolnay/rust-toolchain@stable
         with:
-          targets: ${{ matrix.platform == 'macos-13' && 'aarch64-apple-darwin,x86_64-apple-darwin' || '' }}
+          targets: ${{ matrix.platform == 'macos-15-intel' && 'aarch64-apple-darwin,x86_64-apple-darwin' || '' }}
 
       - name: Install dependencies (Ubuntu)
         if: matrix.platform == 'ubuntu-22.04'