ci(regression): disable xdist and enforce deterministic test execution

Author: harryswift01

.github/workflows/pr.yaml

@@ -7,6 +7,13 @@ concurrency:
   group: pr-${{ github.ref }}
   cancel-in-progress: true
 
+env:
+  OMP_NUM_THREADS: 1
+  MKL_NUM_THREADS: 1
+  OPENBLAS_NUM_THREADS: 1
+  NUMEXPR_NUM_THREADS: 1
+  PYTHONHASHSEED: 0
+
 jobs:
   unit:
     name: Unit
@@ -34,7 +41,7 @@ jobs:
           python -m pip install -e .[testing]
 
       - name: Pytest (unit) • ${{ matrix.os }}, ${{ matrix.python-version }}
-        run: python -m pytest tests/unit
+        run: python -m pytest tests/unit --cache-clear
 
   discover-systems:
     name: Discover regression systems
@@ -99,11 +106,11 @@ jobs:
         run: |
           python -m pytest tests/regression \
             -m "not slow" \
-            -n auto \
-            --dist=loadscope \
-            -k "${{ matrix.system }}" \
+            --cache-clear \
+            --system "${{ matrix.system }}" \
             -vv \
-            --durations=20
+            --durations=20 \
+            --codeentropy-debug
 
       - name: Upload artifacts (failure)
         if: failure()
@@ -200,6 +207,7 @@ jobs:
       - name: Run coverage
         run: |
           pytest tests/unit \
+            --cache-clear \
             --cov CodeEntropy \
             --cov-report term-missing \
             --cov-report xml \