Install Python headers alongside compiler

Otherwise, the compiler will pick system Python headers instead of the
Conda ones.

Author: DimitriPapadopoulos

.github/workflows/ci.yaml

@@ -35,7 +35,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: Install compilers
-        run: conda install -y c-compiler cxx-compiler
+        run: conda install -y c-compiler cxx-compiler python-devel
 
       - name: Install clang
         if: matrix.platform == 'macos-15-large'
@@ -101,7 +101,7 @@ jobs:
           python-version: "3.13"
 
       - name: Install compilers
-        run: conda install -y c-compiler cxx-compiler
+        run: conda install -y c-compiler cxx-compiler python-devel
 
       - name: Install numcodecs
         run: |
@@ -155,7 +155,7 @@ jobs:
           python-version: "3.13"
 
       - name: Install compilers
-        run: conda install -y c-compiler cxx-compiler
+        run: conda install -y c-compiler cxx-compiler python-devel
 
       - name: Install numcodecs and Zarr
         run: |