Fix Windows CI Swift setup error

- Replace swift-actions/setup-swift@v2 with SwiftyLab/setup-swift@latest for Windows
- Use Swift 5.10 instead of 6.0 for better Windows compatibility
- SwiftyLab/setup-swift has confirmed Windows support and active maintenance
- Swift 5.10.1 officially supports Windows as of 2024

This resolves the "Version '6.0' is not available" error on Windows runners.

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

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

Author: miriamkw

.github/workflows/ci.yml

@@ -40,9 +40,9 @@ jobs:
 
       - name: Set up Swift (Windows)
         if: matrix.os == 'windows-latest'
-        uses: swift-actions/setup-swift@v2
+        uses: SwiftyLab/setup-swift@latest
         with:
-          swift-version: "6.0"
+          swift-version: "5.10"
 
       - name: Install dependencies
         run: |