Add no-GIL interpreter support

Add `pytest-run-parallel` as dependency, test no-GIL interpreters in CI, and
mark Cython module as safe for freethreaded interpreters.

.github/workflows/test.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       matrix:
         os: ["ubuntu-latest", "windows-latest", "macos-latest"]
-        py: ["3.14-dev", "3.13", "3.12", "3.11", "3.10", "3.9", "3.8"]
+        py: ["3.14", "3.14t", "3.13", "3.13t", "3.12", "3.11", "3.10", "3.9", "3.8"]
 
     runs-on: ${{ matrix.os }}
     name: Run test with Python ${{ matrix.py }} on ${{ matrix.os }}
@@ -41,12 +41,12 @@ jobs:
       - name: Test (C extension)
         shell: bash
         run: |
-          pytest -v test
+          PYTHON_GIL=0 pytest -v test
 
       - name: Test (pure Python fallback)
         shell: bash
         run: |
-          MSGPACK_PUREPYTHON=1 pytest -v test
+          PYTHON_GIL=0 MSGPACK_PUREPYTHON=1 pytest -v test
 
       - name: build packages
         shell: bash

.github/workflows/wheel.yml

@@ -32,8 +32,9 @@ jobs:
         uses: pypa/cibuildwheel@v2.23.3
         env:
           CIBW_TEST_REQUIRES: "pytest"
-          CIBW_TEST_COMMAND: "pytest {package}/test"
+          CIBW_TEST_COMMAND: "PYTHON_GIL=0 pytest {package}/test"
           CIBW_SKIP: "pp* cp38-macosx_*"
+          CIBW_ENABLE: cpython-freerelease
 
       - name: Build sdist
         if: runner.os == 'Linux' && runner.arch == 'X64'