CI: Upload regression test results as artifact

Author: alexdewar

.github/workflows/cargo-test.yml

@@ -21,7 +21,20 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - uses: actions-rust-lang/setup-rust-toolchain@v1
-      - run: cargo test --verbose
+      - name: Run cargo test
+        shell: bash
+        env:
+          MUSE2_TEST_OUTPUT_DIR: test_results
+        run: |
+          mkdir $MUSE2_TEST_OUTPUT_DIR
+          cargo test --verbose
+
+      # Upload regression test results for analysis
+      - uses: actions/upload-artifact@v4
+        if: "!cancelled()"
+        with:
+          name: muse2_test_results_${{ matrix.os }}
+          path: test_results
 
       - if: ${{ matrix.coverage }}
         uses: ./.github/actions/codecov