feat(ci): add auto-format workflow

Automatically runs 'make fmt' on push and pull requests, then commits
any formatting changes back to the branch.

Author: d0ugal

.github/workflows/auto-format.yml

@@ -0,0 +1,37 @@
+name: Auto Format
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  format:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.head_ref || github.ref }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: 'stable'
+
+      - name: Run make fmt
+        run: make fmt
+
+      - name: Commit changes
+        uses: stefanzweifel/git-auto-commit-action@v5
+        with:
+          commit_message: 'chore: apply code formatting changes'
+          commit_user_name: 'github-actions[bot]'
+          commit_user_email: 'github-actions[bot]@users.noreply.github.com'
+          commit_options: '--no-verify --no-gpg-sign'
+          skip_dirty_check: false
+