Bump actions/checkout from v4.3.1 to v6.0.2 for Node 24

GitHub Actions has deprecated Node.js 20; runners log a warning on v4.3.1 and will force-migrate to Node 24 in June 2026, with full removal in September 2026. v6.0.2 is the current latest and advertises Node 24 support. persist-credentials: false is unchanged across all three jobs.

Author: d4rken

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 10
     steps:
       - name: Checkout
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           persist-credentials: false
 
@@ -40,7 +40,7 @@ jobs:
     timeout-minutes: 10
     steps:
       - name: Checkout
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           persist-credentials: false
 
@@ -68,7 +68,7 @@ jobs:
           - standalone
     steps:
       - name: Checkout
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           persist-credentials: false