fix(ci): use branch_to_build input for checkout and artifact naming

.github/workflows/build-wheels.yml

@@ -16,7 +16,7 @@ on:
         default: ''
 
 concurrency:
-  group: build-${{ github.ref }}
+  group: build-${{ github.ref }}-${{ github.event.inputs.branch_to_build }}
   cancel-in-progress: true
 
 jobs:
@@ -31,10 +31,23 @@ jobs:
     env:
       CMAKE_BUILD_PARALLEL_LEVEL: '4'
     steps:
+      - name: Determine target branch
+        id: branch
+        run: |
+          NAME="${{ github.event.inputs.branch_to_build }}"
+          if [ -z "$NAME" ]; then
+            NAME="${{ github.ref_name }}"
+          fi
+          # Sanitize for artifact naming (replace / with -)
+          SAFE_NAME=$(echo "$NAME" | tr '/' '-')
+          echo "name=$NAME" >> $GITHUB_OUTPUT
+          echo "safe_name=$SAFE_NAME" >> $GITHUB_OUTPUT
+          echo "Target branch: $NAME (safe: $SAFE_NAME)"
+
       - name: Checkout
         uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.inputs.branch_to_build || github.ref }}
+          ref: ${{ steps.branch.outputs.name }}
           submodules: recursive
 
       - name: Set up Python ${{ matrix.python }}
@@ -67,7 +80,7 @@ jobs:
       - name: Upload wheel artifact
         uses: actions/upload-artifact@v4
         with:
-          name: mlx-${{ github.ref_name }}-py${{ matrix.python }}-wheels
+          name: mlx-${{ steps.branch.outputs.safe_name }}-py${{ matrix.python }}-wheels
           path: ./wheels/*.whl
           retention-days: 30
           if-no-files-found: error