[version] add __variant__

Specifies origin and OS of executable files.
For example 'stable/windows'.

.github/workflows/executables.yml

@@ -42,7 +42,9 @@ jobs:
         architecture: ${{ matrix.architecture }}
 
     - name: Date
-      run: echo "DATE=$(date '+${{ env.DATE_FORMAT }}')" >> "$GITHUB_ENV"
+      run: |
+        echo "DATE=$(date '+${{ env.DATE_FORMAT }}')" >> "$GITHUB_ENV"
+        echo "LABEL=$(python ./scripts/pyinstaller.py --print --os '${{ matrix.os }}' --arch '${{ matrix.architecture }}')" >> "$GITHUB_ENV"
 
     - name: Update Version
       # use Python since its behavior is consistent across operating systems
@@ -56,13 +58,17 @@ jobs:
             r'\b(__version__ = "[^"]+)',
             r"\1:${{ env.DATE }}",
             content)
+        content = re.sub(
+            r'\b(__variant__ =).+',
+            r'\1 "dev/${{ env.LABEL }}"',
+            content)
         with open(path, "w") as fp:
             fp.write(content)
 
     - name: Build executable
       run: |
         pip install requests requests[socks] yt-dlp pyyaml ${{ matrix.python-packages }} pyinstaller
-        python ./scripts/pyinstaller.py --os '${{ matrix.os }}' --arch '${{ matrix.architecture }}'
+        python ./scripts/pyinstaller.py --label '${{ env.LABEL }}'
 
     - uses: actions/upload-artifact@v4
       with: