Switch to Xcode 16.4

.github/workflows/main.yml

@@ -18,7 +18,7 @@ concurrency:
 
 env:
   # Path format pulled from https://github.com/actions/runner-images/blob/main/images/macos/macos-15-Readme.md#xcode
-  DEVELOPER_DIR: /Applications/Xcode_16.3.app
+  DEVELOPER_DIR: /Applications/Xcode_16.4.app
 
 jobs:
   build_and_test:
@@ -31,7 +31,7 @@ jobs:
     strategy:
       matrix:
         # Add additional Xcode versions here if necessary.
-        xcode: ["Xcode_16.3"]
+        xcode: ["Xcode_16.4"]
 
     steps:
       - name: Set Xcode version

.xcode-version

@@ -1 +1 @@
-Xcode 16.3
+Xcode 16.4