Stabilize CI matrix and pin NumPy baseline to 1.26.4

Simplify CI to stable baseline only per maintainer guidance:

CI Matrix Changes:
- Keep ONLY Python 3.10 + NumPy 1.26.4 (primary baseline)
- Keep ONLY Python 3.11 + NumPy 1.26.4 (backward compatibility)
- Remove all NumPy 2.x testing (upstream dependency instability)
- Remove Python 3.12 entirely (wait for stable ecosystem)
- Final matrix: 2 jobs only

Dependency Changes:
- Pin numpy to exact stable version: ==1.26.4
- Revert numcodecs: >=0.15,<0.16 (stable baseline)
- Keep zarr: >=2.18.3,<3.0.0

Rationale:
- Establishes reliable CI baseline without upstream breakages
- Removes experimental/transitional NumPy 2.x environments
- Focuses on proven stable ecosystem
- No application code changes - environment only

Author: adilraza99

.github/workflows/tests.yml

@@ -11,19 +11,8 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        python-version: ["3.10", "3.11", "3.12"]
-        numpy-version:
-          - "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"
+        python-version: ["3.10", "3.11"]
+        numpy-version: ["numpy==1.26.4"]
     runs-on: ubuntu-latest
 
     steps:

pyproject.toml

@@ -21,13 +21,13 @@ license = "MIT"
 
 [tool.poetry.dependencies]
 python = ">=3.10,<3.13"
-numpy = ">=1.26,<2.2"
+numpy = "==1.26.4"
 numba = ">=0.60.0"
 llvmlite = "*"
 scipy = "*"
 pandas = "*"
 zarr = ">=2.18.3, <3.0.0"
-numcodecs = ">=0.16, <0.17"
+numcodecs = ">=0.15, <0.16"
 dask = {version="*", extras=["array"]}
 distributed = "*"
 fsspec = "*"