chore: bump macOS (#1165)

The macOS 13 runner will will be retired by 4 December 2025, with jobs
using macOS 13 failing temporarily during scheduled brownout time
periods starting in November.

[GitHub Actions: macOS 13 runner image is closing
down](https://github.blog/changelog/2025-09-19-github-actions-macos-13-runner-image-is-closing-down/)

---------

Co-authored-by: Henry Schreiner <[email protected]>

Author: DimitriPapadopoulos

.github/workflows/ci.yml

@@ -53,7 +53,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version: ["3.8", "pypy-3.10", "3.13", "3.14"]
-        runs-on: [ubuntu-latest, macos-14]
+        runs-on: [ubuntu-latest, macos-latest]
         cmake-version: ["3.15.x"]
 
         include:
@@ -73,10 +73,10 @@ jobs:
             runs-on: ubuntu-latest
             cmake-version: "3.20.x"
           - python-version: "3.9"
-            runs-on: macos-13
+            runs-on: macos-15-intel
             cmake-version: "3.18.x"
           - python-version: "3.12"
-            runs-on: macos-13
+            runs-on: macos-15-intel
             cmake-version: "3.29.x"
           - python-version: "3.10"
             runs-on: ubuntu-latest
@@ -160,7 +160,8 @@ jobs:
       fail-fast: false
       matrix:
         python-version: ["3.8", "3.11"]
-        runs-on: [ubuntu-latest, macos-13, windows-latest]
+        # TODO: investigate failure with macos-latest (#1167)
+        runs-on: [ubuntu-latest, macos-15-intel, windows-latest]
 
     steps:
       - uses: actions/checkout@v5