Update macOS runners: macos-13 -> macos-15-intel, macos-14 -> macos-latest

macOS-13 runners are deprecated, see:
actions/runner-images#13046

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

Author: ad3002

.github/workflows/ci-rust.yml

@@ -42,9 +42,9 @@ jobs:
         include:
           - os: ubuntu-latest
             target: x86_64-unknown-linux-gnu
-          - os: macos-13
+          - os: macos-15-intel
             target: x86_64-apple-darwin
-          - os: macos-14
+          - os: macos-latest
             target: aarch64-apple-darwin
 
     steps:

.github/workflows/release-rust.yml

@@ -27,12 +27,12 @@ jobs:
             platform: manylinux_2_17_x86_64
 
           # macOS x86_64
-          - os: macos-13
+          - os: macos-15-intel
             target: x86_64-apple-darwin
             platform: macosx_10_12_x86_64
 
           # macOS ARM64 (Apple Silicon)
-          - os: macos-14
+          - os: macos-latest
             target: aarch64-apple-darwin
             platform: macosx_11_0_arm64