ci: bump checkout/setup-python/upload-artifact to Node 24 versions

Node 20 is deprecated on GitHub-hosted runners as of June 2026. Move the
canary and mutation workflows to checkout@v5, setup-python@v6, and
upload-artifact@v5 so we stop emitting the deprecation warning.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: saraswatayu

.github/workflows/live-canary.yml

@@ -10,8 +10,8 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 15
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/checkout@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: "3.13"
       - name: Install dependencies
@@ -24,7 +24,7 @@ jobs:
         run: python -m pytest tests/test_live_contract.py -v -m live
       - name: Upload live canary artifacts
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: live-canary-artifacts
           path: ${{ runner.temp }}/swoop-live-artifacts

.github/workflows/mutation.yml

@@ -7,8 +7,8 @@ jobs:
   mutmut:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/checkout@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: "3.13"
       - name: Install dependencies
@@ -21,7 +21,7 @@ jobs:
         run: mutmut results > mutmut-results.txt || true
       - name: Upload mutation results
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: mutmut-results
           path: mutmut-results.txt