Chore: update black on PR concerning source

.github/workflows/black.yml

@@ -0,0 +1,50 @@
+name: Black autoformat
+
+on:
+  push:
+    branches:
+      - "**"
+    paths:
+      - "ultraplot/**.py"
+      - "ultraplot/**.pyi"
+      - ".github/workflows/black.yml"
+      - ".pre-commit-config.yaml"
+      - "pyproject.toml"
+
+permissions:
+  contents: write
+
+concurrency:
+  group: black-${{ github.ref }}
+  cancel-in-progress: false
+
+jobs:
+  format:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          ref: ${{ github.ref_name }}
+
+      - uses: actions/setup-python@v7
+        with:
+          python-version: "3.14"
+
+      - name: Install Black
+        run: python -m pip install black==26.5.1
+
+      - name: Format Python files
+        run: black ultraplot
+
+      - name: Commit formatting changes
+        run: |
+          if git diff --quiet -- '*.py' '*.pyi'; then
+            echo "Black made no changes."
+            exit 0
+          fi
+
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add --update -- '*.py' '*.pyi'
+          git commit -m "Apply Black formatting"
+          git push

.pre-commit-config.yaml

@@ -6,7 +6,7 @@ ci:
     autofix_prs: false
     autoupdate_commit_msg: '[pre-commit.ci] pre-commit autoupdate'
     autoupdate_schedule: monthly
-    skip: []
+    skip: [black]
     submodules: false
 
 repos: