fix: Update to macos-latest runner for Xcode 16 compatibility

Change from macos-14 to macos-latest to get Xcode 16.0+ which is
required by Microsoft.iOS 18.0.8324.

**Problem**:
- macos-14 runner has Xcode 15.4
- Microsoft.iOS 18.0.8324 requires iOS 18.0 SDK (Xcode 16.0+)
- Build fails with: "error MT0180: This version of Microsoft.iOS requires the iOS 18.0 SDK"

**Solution**:
Use macos-latest runner which should have Xcode 16.0 or later.

**Changes**:
- build.yml: macos-14 → macos-latest (iOS and macOS jobs)
- publish.yml: macos-14 → macos-latest (iOS and macOS jobs)

**Why macos-latest**:
- Always uses the most recent stable macOS runner
- Automatically gets Xcode updates
- More future-proof than pinning to specific version
- GitHub maintains compatibility with latest .NET MAUI

**Note**: If macos-latest doesn't have Xcode 16 yet, we may need to:
- Wait for GitHub to update the image
- Or add /p:MtouchLink=SdkOnly to disable full linking
- Or downgrade Microsoft.iOS package

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.github/workflows/build.yml

@@ -10,7 +10,7 @@ on:
 jobs:
   build-ios:
     name: Build iOS
-    runs-on: macos-14
+    runs-on: macos-latest
 
     steps:
     - name: Checkout code
@@ -41,7 +41,7 @@ jobs:
 
   build-maccatalyst:
     name: Build macOS Catalyst
-    runs-on: macos-14
+    runs-on: macos-latest
 
     steps:
     - name: Checkout code

.github/workflows/publish.yml

@@ -86,7 +86,7 @@ jobs:
 
   build-and-publish-ios:
     name: Build and Publish iOS
-    runs-on: macos-14
+    runs-on: macos-latest
     needs: create-release
 
     steps:
@@ -133,7 +133,7 @@ jobs:
 
   build-and-publish-maccatalyst:
     name: Build and Publish macOS
-    runs-on: macos-14
+    runs-on: macos-latest
     needs: create-release
 
     steps: