Add conservative CI matrix exclusions for NumPy 2.x testing

Implement targeted NumPy 2.x testing strategy to protect stable baseline
while enabling forward compatibility validation:

Matrix changes:
- Python 3.10: ONLY NumPy 1.26.4 (protected stable baseline)
- Python 3.11: NumPy 1.26.4 AND NumPy 2.0 (forward compat testing)
- Python 3.12: ONLY NumPy 1.26.4 (exclude NumPy 2.x due to upstream instability)

Implementation:
- Added matrix.exclude rules for Python 3.10 + numpy~=2.0
- Added matrix.exclude rules for Python 3.12 + numpy~=2.0
- Added NumPy version verification step for debugging/transparency
- Reduces CI matrix from 6 to 4 combinations (more focused)

Rationale:
- Protects Python 3.10 + NumPy 1.26.4 as stable baseline (current Colab)
- Python 3.11 provides middle ground for NumPy 2.x validation
- Python 3.12 + NumPy 2.x excluded due to known zarr/numcodecs instability
- Dependencies (numpy >=1.26,<2.2, numcodecs >=0.16) support both versions

No application code changes - CI workflow only.

Author: adilraza99

.github/workflows/tests.yml

@@ -13,10 +13,17 @@ jobs:
       matrix:
         python-version: ["3.10", "3.11", "3.12"]
         numpy-version:
-          - "numpy==1.26.4"  # current colab version
-          - "numpy~=2.0"  # 2.0 series
+          - "numpy==1.26.4" # current colab version
+          - "numpy~=2.0" # 2.0 series
           # numba (0.60.0) does not yet support numpy 2.1, disable this for now
           # - "numpy~=2.1"  # 2.1 series
+        exclude:
+          # Python 3.10: ONLY test with NumPy 1.26.4 (stable baseline)
+          - python-version: "3.10"
+            numpy-version: "numpy~=2.0"
+          # Python 3.12: ONLY test with NumPy 1.26.4 (upstream wheel/zarr instability)
+          - python-version: "3.12"
+            numpy-version: "numpy~=2.0"
     runs-on: ubuntu-latest
 
     steps:
@@ -32,5 +39,8 @@ jobs:
       - name: Install package
         run: pip install "${{ matrix.numpy-version }}" .[dev]
 
+      - name: Verify NumPy version
+        run: python -c "import numpy; print('NumPy version:', numpy.__version__)"
+
       - name: Run unit tests
         run: pytest -v tests --ignore tests/integration --typeguard-packages=malariagen_data,malariagen_data.anoph