Add GitHub Actions CI for macOS

Two jobs run on every push/PR against main and dev:
- C++ build + tests: brew installs wxwidgets and libarchive,
  configures CMake with BUILD_TESTS=ON, builds all four targets,
  runs ./build/mrtk_tests, uploads mrtk_cli and mrtk_gui as
  artifacts (14-day retention).
- Python tests: installs pytest, requests, packaging on Python
  3.12 and runs pytest against tests/test_core_logic.py.

Author: Tianyu Song

.github/workflows/ci.yml

@@ -0,0 +1,57 @@
+name: CI
+
+on:
+  push:
+    branches: [main, dev]
+  pull_request:
+    branches: [main, dev]
+
+jobs:
+  cpp-build-and-test:
+    name: C++ build + tests (macOS)
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install build dependencies (Homebrew)
+        run: |
+          brew update
+          brew install wxwidgets libarchive
+
+      - name: Configure CMake
+        run: cmake -S . -B build -DBUILD_TESTS=ON -DCMAKE_BUILD_TYPE=Release
+
+      - name: Build (mrtk_core, mrtk_cli, mrtk_gui, mrtk_tests)
+        run: cmake --build build -j
+
+      - name: Run regression tests
+        run: ./build/mrtk_tests
+
+      - name: Upload built binaries
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: mrtk-macos-${{ github.sha }}
+          path: |
+            build/mrtk_cli
+            build/mrtk_gui
+          if-no-files-found: warn
+          retention-days: 14
+
+  python-tests:
+    name: Python tests (macOS)
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install Python dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install pytest requests packaging
+
+      - name: Run pytest
+        run: python -m pytest tests/test_core_logic.py -v