ci: add explicit pixi env

Author: ahoarau

.github/workflows/ci-pixi.yml

@@ -31,6 +31,7 @@ jobs:
       matrix:
         build_type: [Release, Debug]
         cxx_std: [17, 20]
+        pixi_environment: [default]
         os: [ubuntu-22.04, ubuntu-24.04, macos-15-intel, macos-26, windows-2022, windows-2025]
 
     steps:
@@ -44,33 +45,32 @@ jobs:
       - name: Install Pixi
         uses: prefix-dev/setup-pixi@v0.9.3
         with:
-          cache: false
-          pixi-version: latest
+          environments: default
 
       - name: Install Pixi environment
-        run: pixi install
+        run: pixi -e default install
 
       - name: Configure
-        run: pixi run configure --fresh --log-level=DEBUG
+        run: pixi run -e default configure --fresh --log-level=DEBUG
 
       - name: Build
-        run: pixi run build --verbose --parallel 1
+        run: pixi run -e default build --verbose --parallel 1
 
       - name: Install
-        run: pixi run install
+        run: pixi run -e default install
 
       - name: Test Python import
-        run: pixi run test-import-python
+        run: pixi run -e default test-import-python
 
       - name: Run C++ tests
         if: ${{ !(startsWith(matrix.os, 'windows-') && matrix.build_type == 'Debug') }}
-        run: pixi run test
+        run: pixi run -e default test
 
       - name: Run packaging tests
-        run: pixi run test-packaging
+        run: pixi run -e default test-packaging
 
       - name: Uninstall
-        run: pixi run uninstall
+        run: pixi run -e default uninstall
 
   pixi-build:
     name: Pixi Build CI
@@ -85,10 +85,11 @@ jobs:
       - name: Install Pixi
         uses: prefix-dev/setup-pixi@v0.9.3
         with:
+          cache: false
           environments: test-pixi-build
 
       - name: Run Pixi build test
-        run: pixi run test-pixi-build test
+        run: pixi run -e test-pixi-build test
 
   prek:
     name: Prek CI