refactor: use reusable workflow to avoid code duplication

.github/workflows/build-reusable.yml

@@ -0,0 +1,92 @@
+name: Reusable Build
+
+on:
+  workflow_call:
+    inputs:
+      ref:
+        description: 'Git ref to build'
+        required: false
+        type: string
+        default: ''
+
+jobs:
+  build:
+    name: Build ${{ matrix.os }}
+    strategy:
+      matrix:
+        include:
+          - os: ubuntu-latest
+            python: '3.11'
+          - os: macos-latest
+            python: '3.11'
+    runs-on: ${{ matrix.os }}
+    
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+          submodules: recursive
+      
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python }}
+      
+      - name: Install uv
+        uses: astral-sh/setup-uv@v4
+      
+      - name: Install system dependencies (Ubuntu)
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libomp-dev libboost-all-dev protobuf-compiler libzmq3-dev
+      
+      - name: Install system dependencies (macOS)
+        if: runner.os == 'macOS'
+        run: |
+          brew install llvm libomp boost protobuf zeromq
+      
+      - name: Build packages
+        run: |
+          # Build core (platform independent)
+          if [ "${{ matrix.os }}" == "ubuntu-latest" ]; then
+            cd packages/leann-core
+            uv build
+            cd ../..
+          fi
+          
+          # Build HNSW backend
+          cd packages/leann-backend-hnsw
+          uv pip install --system -r pyproject.toml --extra build
+          if [ "${{ matrix.os }}" == "macos-latest" ]; then
+            CC=$(brew --prefix llvm)/bin/clang CXX=$(brew --prefix llvm)/bin/clang++ uv build
+          else
+            uv build
+          fi
+          cd ../..
+          
+          # Build DiskANN backend
+          cd packages/leann-backend-diskann
+          uv pip install --system -r pyproject.toml --extra build
+          if [ "${{ matrix.os }}" == "macos-latest" ]; then
+            CC=$(brew --prefix llvm)/bin/clang CXX=$(brew --prefix llvm)/bin/clang++ uv build
+          else
+            uv build
+          fi
+          cd ../..
+          
+          # Build meta package (platform independent)
+          if [ "${{ matrix.os }}" == "ubuntu-latest" ]; then
+            cd packages/leann
+            uv build
+            cd ../..
+          fi
+          
+          echo "📦 Built packages:"
+          find packages/*/dist -name "*.whl" -o -name "*.tar.gz" | sort
+      
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: packages-${{ matrix.os }}-${{ matrix.python }}
+          path: packages/*/dist/