ci: bump actions to latest majors (Node 24)

The earlier v4->v5 bump didn't silence the Node 20 deprecation warnings:
actions/upload-artifact@v5 and actions/download-artifact@v5 only have
"preliminary" Node 24 support and still default to Node 20. The runtime
default flips to Node 24 only at v6+. Move every action to its current
latest major (all node24):

  actions/checkout            v5 -> v6
  actions/upload-artifact     v5 -> v7
  actions/download-artifact   v5 -> v8
  softprops/action-gh-release v2 -> v3
  actions/setup-python        v6 (already latest, node24)

All inputs in use remain supported; artifacts stay zipped so upload v7 /
download v8 (direct-upload/decompress changes) and download v8's default
digest-mismatch=error don't affect this workflow.

Author: FeodorFitsner

.github/workflows/build-python-version.yml

@@ -34,7 +34,7 @@ jobs:
     runs-on: macos-26
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Derive short Python version
         shell: bash
@@ -72,7 +72,7 @@ jobs:
           bash ./package-macos-for-dart.sh . "$PYTHON_VERSION"
 
       - name: Upload Darwin build artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v7
         with:
           name: python-darwin-${{ env.PYTHON_VERSION }}
           path: darwin/dist/python-*.tar.gz
@@ -83,7 +83,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Derive short Python version
         shell: bash
@@ -125,7 +125,7 @@ jobs:
         run: python3 -m unittest discover -s android/tests -t android/tests -v
 
       - name: Upload build artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v7
         with:
           name: python-android-${{ env.PYTHON_VERSION }}
           path: android/dist/python-android-*.tar.gz
@@ -136,7 +136,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Derive short Python version
         shell: bash
@@ -158,7 +158,7 @@ jobs:
           bash ./package-for-linux.sh aarch64 ""
 
       - name: Upload build artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v7
         with:
           name: python-linux-${{ env.PYTHON_VERSION }}
           path: linux/python-linux-dart-*.tar.gz
@@ -168,7 +168,7 @@ jobs:
     name: Build Python for Windows
     runs-on: windows-2022
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Derive short Python version
         shell: pwsh
@@ -189,7 +189,7 @@ jobs:
             -PythonVersionShort "${{ env.PYTHON_VERSION_SHORT }}"
 
       - name: Upload build artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v7
         with:
           name: python-windows-${{ env.PYTHON_VERSION }}
           path: windows/python-windows-for-dart-*.zip

.github/workflows/build-python.yml

@@ -49,14 +49,14 @@ jobs:
       contents: write
     steps:
       - name: Download all build artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v8
         with:
           pattern: python-*
           path: release-artifacts
           merge-multiple: true
 
       - name: Publish all artifacts to release
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@v3
         with:
           tag_name: ${{ inputs.release_date }}
           name: ${{ inputs.release_date }}