refactor: switch swift-format workflow to macOS

- Change from Linux container to macOS runner (matches Point-Free approach)
- Use Homebrew to install swift-format instead of building from source
- Remove unnecessary caching, git configuration, and ref handling
- Reduces workflow time from 8+ minutes to ~1 minute
- Eliminates detached HEAD warnings from container environment

Author: coenttb

.github/workflows/swift-format.yml

@@ -12,40 +12,18 @@ concurrency:
 jobs:
   swift_format:
     name: swift-format
-    runs-on: ubuntu-latest
-    container: swift:6.2
+    runs-on: macos-latest
     permissions:
       contents: write
     steps:
       - uses: actions/checkout@v5
-        with:
-          ref: ${{ github.head_ref || github.ref_name }}
-
-      - name: Cache swift-format
-        id: cache-swift-format
-        uses: actions/cache@v4
-        with:
-          path: /usr/local/bin/swift-format
-          key: ${{ runner.os }}-swift-format-${{ hashFiles('.github/workflows/swift-format.yml') }}
 
       - name: Install swift-format
-        if: steps.cache-swift-format.outputs.cache-hit != 'true'
-        run: |
-          git clone --depth 1 --branch main https://github.com/apple/swift-format.git
-          cd swift-format
-          swift build -c release
-          cp .build/release/swift-format /usr/local/bin/
-          cd ..
-          rm -rf swift-format
+        run: brew install swift-format
 
       - name: Format
         run: swift-format format --ignore-unparsable-files --recursive --in-place Sources Tests
 
-      - name: Configure git for container
-        run: |
-          git config --global --add safe.directory $GITHUB_WORKSPACE
-          git checkout main
-
       - uses: stefanzweifel/git-auto-commit-action@v7
         with:
           commit_message: Run swift-format