ci: add Swift example builds on macOS

Auto-discover Swift examples via example/*/Package.swift alongside
the existing zig and cmake discovery. The new build-examples-swift
job runs on macOS, builds the xcframework with zig build -Demit-lib-vt,
then runs swift run in each example directory to verify the
xcframework links and functions correctly end-to-end.

.github/workflows/test.yml

@@ -89,6 +89,7 @@ jobs:
       - build-examples-zig
       - build-examples-cmake
       - build-examples-cmake-windows
+      - build-examples-swift
       - build-cmake
       - build-flatpak
       - build-libghostty-vt
@@ -181,6 +182,7 @@ jobs:
     outputs:
       zig: ${{ steps.list.outputs.zig }}
       cmake: ${{ steps.list.outputs.cmake }}
+      swift: ${{ steps.list.outputs.swift }}
     steps:
       - name: Checkout code
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
@@ -193,6 +195,9 @@ jobs:
           cmake=$(ls example/*/CMakeLists.txt 2>/dev/null | xargs -n1 dirname | xargs -n1 basename | jq -R -s -c 'split("\n") | map(select(. != ""))')
           echo "$cmake" | jq .
           echo "cmake=$cmake" >> "$GITHUB_OUTPUT"
+          swift=$(ls example/*/Package.swift 2>/dev/null | xargs -n1 dirname | xargs -n1 basename | jq -R -s -c 'split("\n") | map(select(. != ""))')
+          echo "$swift" | jq .
+          echo "swift=$swift" >> "$GITHUB_OUTPUT"
 
   build-examples-zig:
     strategy:
@@ -290,6 +295,49 @@ jobs:
           cmake -B build -DFETCHCONTENT_SOURCE_DIR_GHOSTTY=${{ github.workspace }}
           cmake --build build
 
+  build-examples-swift:
+    strategy:
+      fail-fast: false
+      matrix:
+        dir: ${{ fromJSON(needs.list-examples.outputs.swift) }}
+    name: Example ${{ matrix.dir }}
+    runs-on: namespace-profile-ghostty-macos-tahoe
+    needs: [test, list-examples]
+    env:
+      ZIG_LOCAL_CACHE_DIR: /Users/runner/zig/local-cache
+      ZIG_GLOBAL_CACHE_DIR: /Users/runner/zig/global-cache
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - name: Setup Cache
+        uses: namespacelabs/nscloud-cache-action@a90bb5d4b27522ce881c6e98eebd7d7e6d1653f9 # v1.4.2
+        with:
+          cache: |
+            xcode
+          path: |
+            /Users/runner/zig
+
+      # TODO(tahoe): https://github.com/NixOS/nix/issues/13342
+      - uses: DeterminateSystems/nix-installer-action@main
+        with:
+          determinate: true
+      - uses: cachix/cachix-action@1eb2ef646ac0255473d23a5907ad7b04ce94065c # v17
+        with:
+          name: ghostty
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+
+      - name: Xcode Select
+        run: sudo xcode-select -s /Applications/Xcode_26.3.app
+
+      - name: Build XCFramework
+        run: nix develop -c zig build -Demit-lib-vt
+
+      - name: Build and Run Example
+        run: |
+          cd example/${{ matrix.dir }}
+          swift run
+
   build-cmake:
     runs-on: namespace-profile-ghostty-sm
     needs: test