Skip test_pyzstd when pyzstd cannot be imported - #845

On Python 3.14, pyzstd imports the standard library's compression.zstd, which needs the _zstd extension module. Alpine's i386 Python does not ship it, so importing pyzstd raised ModuleNotFoundError and aborted test collection. Use pytest.importorskip, as main does (zarr-developers#845).

Assisted-by: ClaudeCode:claude-fable-5.1

* test(checksum32): wrap parametrize itertools.product in tuple

pytest 9 raises PytestRemovedIn10Warning for non-Collection iterables passed to parametrize, which becomes an error under filterwarnings=error and aborts test collection. Same change as 15803df on backport-0.15-zstd-fixes.

Assisted-by: ClaudeCode:claude-fable-5.1

* ci: stop testing the 0.16.x line against zarr-python main

zarr-python main now requires Python >=3.12, while this line supports Python >=3.11. uv resolves all dependency groups together, so the test-zarr-main group made every uv invocation fail with an unsatisfiable resolution (seen in the i386 workflow). A maintenance line does not need to track zarr-python main, so remove the group, its pixi tasks, and its CI matrix entry.

Assisted-by: ClaudeCode:claude-fable-5.1

* ci: replace the macos-13 runner with macos-15-large

macos-13 runners are no longer available. macos-15-large is still an Intel runner, so x86 coverage is preserved. macOS 15's dyld rejects the duplicate LC_RPATH entries that the conda-forge compilers produce, so add the same deduplication step used on backport-0.15-zstd-fixes (64eade5, 7ae0f4b).

Assisted-by: ClaudeCode:claude-fable-5.1

* ci(docs): build on ubuntu-24.04 on Read the Docs

Read the Docs removed the ubuntu-20.04 build image.

Assisted-by: ClaudeCode:claude-fable-5.1

* ci: stop pinning clang below 17 on the Intel macOS runner

The pin downgraded the conda-forge compiler to clang 14, which cannot parse the macOS 15 SDK headers on macos-15-large (math.h: '_Float16 is not supported on this target'), so every extension build failed. Use the clang that the conda-forge c-compiler package installs instead.

Assisted-by: ClaudeCode:claude-fable-5.1

* ci(i386): install zfpy with uv pip instead of uv add

zfp's pyproject.toml has no [project] table, so 'uv add "zfpy @ ./zfp"' fails with 'No project table found'. Install the locally built zfpy into the environment with 'uv pip install ./zfp', as main does. Because zfpy is no longer recorded in pyproject.toml, keep the same virtual environment for the numcodecs install and run pytest with --no-sync so uv does not re-resolve the environment.

Assisted-by: ClaudeCode:claude-fable-5.1

* ci(i386): stop installing pcodec in the i386 job

This workflow has no matrix, so the python-version conditional always took the branch that installs pcodec. pcodec has no i386 wheel and its source build produces a wheel tagged linux_x86_64, which uv refuses to install in the i386 Alpine environment. Install without pcodec, as main does; the pcodec tests are skipped when it is missing.

Assisted-by: ClaudeCode:claude-fable-5.1

* test(pyzstd): skip test_pyzstd when pyzstd cannot be imported

On Python 3.14, pyzstd imports the standard library's compression.zstd, which needs the _zstd extension module. Alpine's i386 Python does not ship it, so importing pyzstd raised ModuleNotFoundError and aborted test collection. Use pytest.importorskip, as main does (#845).

Assisted-by: ClaudeCode:claude-fable-5.1

* ci(codecov): compare project coverage against the base commit

codecov/project has failed on every recent commit of this line, including the 0.16.5 release, at 98.68% against a 100% target. The uncovered lines are in numcodecs/zarr3.py and the crc32c fallback paths, which the coverage-uploading jobs do not exercise. Set the project target to auto so the check fails only when a change lowers coverage. The patch target stays at 100%.

Assisted-by: ClaudeCode:claude-fable-5.1