Add aggregation jobs to maxtrix workflows

.github/workflows/tests.yml

@@ -57,3 +57,15 @@ jobs:
           name: codecov-umbrella
           token: ${{ secrets.CODECOV_TOKEN }}
           verbose: true
+
+  # Single stable status check for the whole test matrix, so branch protection
+  # doesn't need updating every time the OS/Python matrix changes.
+  all-tests-passed:
+    name: All Tests Passed
+    if: always()
+    needs: [tests]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Fail if any matrix job did not succeed
+        if: needs.tests.result != 'success'
+        run: exit 1

.github/workflows/typecheck.yml

@@ -36,3 +36,15 @@ jobs:
 
       - name: Check typing using mypy
         run: uv run --no-default-groups --group validate mypy .
+
+  # Single stable status check for the whole type-check matrix, so branch
+  # protection doesn't need updating every time the Python matrix changes.
+  all-type-checks-passed:
+    name: All Type Checks Passed
+    if: always()
+    needs: [type-check]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Fail if any matrix job did not succeed
+        if: needs['type-check'].result != 'success'
+        run: exit 1