ci(regression): warm up systems before baseline comparison

Author: harryswift01

.github/workflows/pr.yaml

@@ -67,7 +67,7 @@ jobs:
     name: Regression (fast) • ${{ matrix.system }}
     needs: [unit, discover-systems]
     runs-on: ubuntu-24.04
-    timeout-minutes: 35
+    timeout-minutes: 45
 
     strategy:
       fail-fast: false
@@ -95,6 +95,15 @@ jobs:
           python -m pip install --upgrade pip
           python -m pip install -e .[testing]
 
+      - name: Warm up regression system
+        run: |
+          python -m pytest tests/regression \
+            -m "not slow" \
+            -n auto \
+            --dist=loadscope \
+            -k "${{ matrix.system }}" \
+            -q || true
+
       - name: Run fast regression tests (per system)
         run: |
           python -m pytest tests/regression \