chore: Update GitHub Actions to Node.js 24 compatible versions

- actions/checkout: v3/v4/v5 → v6
- actions/upload-artifact: v3/v4 → v6
- actions/download-artifact: v4/v5 → v7
- Maintains r-lib/actions at v2 (unchanged)

Author: ms609

.github/workflows/ASan.yml

@@ -49,7 +49,7 @@ jobs:
       ASAN_OPTIONS: detect_container_overflow=1:verify_asan_link_order=0
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Initialize ASan configuration
         run: |

.github/workflows/R-CMD-check.yml

@@ -52,7 +52,7 @@ jobs:
 
     steps:
       - name: Checkout git repo
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Temporarily bump package version
         run: |
@@ -112,7 +112,7 @@ jobs:
 
     steps:
       - name: Checkout git repo
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Temporarily bump package version
         run: |
@@ -246,12 +246,12 @@ jobs:
 
     steps:
       - name: Checkout PR branch
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           path: pr
 
       - name: Checkout target branch
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: ${{ github.event.pull_request.base.ref || 'main' }}
           path: main
@@ -301,14 +301,14 @@ jobs:
 
       - name: Upload PR benchmark results
         if: failure()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: pr-benchmark-results
           path: pr/pr-benchmark-results/*.bench.Rds
 
       - name: Upload main benchmark results
         if: failure()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: main-benchmark-results
           path: pr/main-benchmark-results/*.bench.Rds

.github/workflows/copilot-setup-steps.yml

@@ -26,7 +26,7 @@ jobs:
     # If you do not check out your code, Copilot will do this for you.
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up R
         uses: r-lib/actions/setup-r@v2
@@ -55,7 +55,7 @@ jobs:
             check
 
       - name: Checkout TreeTools source (for debugging support)
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: ms609/TreeTools
           path: TreeTools-source

.github/workflows/update-csl.yml

@@ -13,7 +13,7 @@ jobs:
   update-csl:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Download latest CSL file
         run: |