chore: upgrade GitHub Actions to Node.js 24 versions

checkout v4→v6, setup-python v5→v6. Resolves Node.js 20 deprecation
warnings.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: baijum

.github/workflows/docs.yml

@@ -15,9 +15,9 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: "3.12"
 

.github/workflows/test.yml

@@ -10,10 +10,10 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: '3.12'
           cache: pip