chore: remove Swift/iOS remnants

- Delete .github/workflows/ci.yml (Swift CI on macOS)
- Remove 'Swift Code Reviewer' agent from code-reviewer.agent.md
- Remove 'migration' label (C# → Swift) from gh-tickets SKILL

.github/workflows/ci.yml

@@ -1,86 +0,0 @@
-name: CI – Swift Tests (macOS)
-
-on:
-  workflow_dispatch:
-
-jobs:
-  test:
-    name: Swift Tests (macOS)
-    runs-on: macos-15
-
-    env:
-      FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
-
-    defaults:
-      run:
-        working-directory: Migration
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Select Xcode 16.3
-        run: sudo xcode-select -s /Applications/Xcode_16.3.app/Contents/Developer
-
-      - name: Show Swift version
-        run: swift --version
-
-      - name: Install SwiftLint
-        run: brew install swiftlint
-
-      - name: Run SwiftLint
-        run: swiftlint lint --reporter github-actions-logging
-
-      - name: Build
-        run: swift build 2>&1 | tee build.log; exit ${PIPESTATUS[0]}
-
-      - name: Run tests
-        run: swift test 2>&1 | tee test.log; exit ${PIPESTATUS[0]}
-
-      - name: Start MockServer
-        run: |
-          cd "$GITHUB_WORKSPACE/MockServer"
-          npm install --silent
-          node server.js &
-          echo "MOCK_PID=$!" >> "$GITHUB_ENV"
-          sleep 2
-          curl -sf http://localhost:3000/auth/login \
-            -X POST -H 'Content-Type: application/json' \
-            -d '{"username":"ci","password":"ci"}' > /dev/null
-          echo "MockServer running on :3000"
-
-      - name: Run integration tests
-        env:
-          MOCKSERVER_INTEGRATION: "1"
-        run: swift test --filter MockServerIntegration 2>&1 | tee integration.log; exit ${PIPESTATUS[0]}
-
-      - name: Stop MockServer
-        if: always()
-        run: kill $MOCK_PID 2>/dev/null || true
-
-  demonstrator:
-    name: Demonstrator Build + Test (macOS)
-    runs-on: macos-15
-
-    env:
-      FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
-
-    defaults:
-      run:
-        working-directory: Demonstrator/App
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Select Xcode 16.3
-        run: sudo xcode-select -s /Applications/Xcode_16.3.app/Contents/Developer
-
-      - name: Show Swift version
-        run: swift --version
-
-      - name: Build
-        run: swift build 2>&1 | tee build.log; exit ${PIPESTATUS[0]}
-
-      - name: Run tests
-        run: swift test 2>&1 | tee test.log; exit ${PIPESTATUS[0]}