Fix GitHub Actions: Use full path to Blender executable in BlenderKit containers

Problem:
- After switching to blenderkit/headless-blender images, workflow was failing with 'blender: not found' (exit code 127)
- The 'blender' command is not in PATH in these containers

Solution:
- Blender is installed at /home/headless/blender/blender in BlenderKit containers
- Updated all workflow steps to use full path: /home/headless/blender/blender
- Applied to all three jobs:
  - test-blender-5 (Blender 5.0)
  - test-blender-4 (Blender 4.2 LTS)
  - quick-check (Quick smoke test)

Changes:
- Verify Blender version: blender → /home/headless/blender/blender
- Install Python dependencies: blender → /home/headless/blender/blender
- Run test suite: blender → /home/headless/blender/blender

Author: zbuc

.github/workflows/blender-tests.yml

@@ -24,13 +24,13 @@ jobs:
 
       - name: Verify Blender version
         run: |
-          blender --version
-          blender --background --python-expr "import sys; print(f'Python: {sys.version}')"
+          /home/headless/blender/blender --version
+          /home/headless/blender/blender --background --python-expr "import sys; print(f'Python: {sys.version}')"
 
       - name: Install Python dependencies in Blender
         run: |
           # Find Blender's Python executable
-          BLENDER_PYTHON=$(blender --background --python-expr "import sys; print(sys.executable)" 2>&1 | grep -oP '/[^ ]+python[0-9.]*' | head -1)
+          BLENDER_PYTHON=$(/home/headless/blender/blender --background --python-expr "import sys; print(sys.executable)" 2>&1 | grep -oP '/[^ ]+python[0-9.]*' | head -1)
           echo "Blender Python: $BLENDER_PYTHON"
 
           # Verify pip is available
@@ -45,7 +45,7 @@ jobs:
       - name: Run test suite
         run: |
           cd blender_blocking
-          blender --background --python test_runner.py
+          /home/headless/blender/blender --background --python test_runner.py
 
       - name: Upload test logs on failure
         if: failure()
@@ -69,20 +69,20 @@ jobs:
 
       - name: Verify Blender version
         run: |
-          blender --version
-          blender --background --python-expr "import sys; print(f'Python: {sys.version}')"
+          /home/headless/blender/blender --version
+          /home/headless/blender/blender --background --python-expr "import sys; print(f'Python: {sys.version}')"
 
       - name: Install Python dependencies in Blender
         run: |
-          BLENDER_PYTHON=$(blender --background --python-expr "import sys; print(sys.executable)" 2>&1 | grep -oP '/[^ ]+python[0-9.]*' | head -1)
+          BLENDER_PYTHON=$(/home/headless/blender/blender --background --python-expr "import sys; print(sys.executable)" 2>&1 | grep -oP '/[^ ]+python[0-9.]*' | head -1)
           echo "Blender Python: $BLENDER_PYTHON"
           $BLENDER_PYTHON -m pip install numpy opencv-python Pillow scipy
           $BLENDER_PYTHON -c "import numpy, cv2, PIL, scipy; print('Dependencies installed')"
 
       - name: Run test suite
         run: |
           cd blender_blocking
-          blender --background --python test_runner.py
+          /home/headless/blender/blender --background --python test_runner.py
 
       - name: Upload test logs on failure
         if: failure()
@@ -106,10 +106,10 @@ jobs:
 
       - name: Install dependencies
         run: |
-          BLENDER_PYTHON=$(blender --background --python-expr "import sys; print(sys.executable)" 2>&1 | grep -oP '/[^ ]+python[0-9.]*' | head -1)
+          BLENDER_PYTHON=$(/home/headless/blender/blender --background --python-expr "import sys; print(sys.executable)" 2>&1 | grep -oP '/[^ ]+python[0-9.]*' | head -1)
           $BLENDER_PYTHON -m pip install numpy opencv-python Pillow scipy
 
       - name: Run quick tests
         run: |
           cd blender_blocking
-          blender --background --python test_runner.py -- --quick
+          /home/headless/blender/blender --background --python test_runner.py -- --quick