CI: auto-create GitHub release on version tags

.github/workflows/ci.yml

@@ -67,3 +67,35 @@ jobs:
 
       - name: Publish to NuGet
         run: dotnet nuget push "./artifacts/*.nupkg" --api-key "${{ secrets.NUGET_API_KEY }}" --source https://api.nuget.org/v3/index.json --skip-duplicate
+
+  release:
+    needs: publish
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/v')
+    permissions:
+      contents: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      # Pull the section for this tag's version out of CHANGELOG.md
+      # (e.g. tag v0.1.0 -> the "## [0.1.0] — …" block) for the release body.
+      # Falls back to a minimal note if the section isn't found.
+      - name: Build release notes
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          awk -v ver="$version" '
+            $0 ~ "^## \\[" ver "\\]" { capture = 1; next }
+            capture && /^## \[/ { exit }
+            capture && /^\[.*\]: / { exit }
+            capture { print }
+          ' CHANGELOG.md > release-notes.md
+          if [ ! -s release-notes.md ]; then
+            echo "Release $GITHUB_REF_NAME" > release-notes.md
+          fi
+
+      - name: Create GitHub release
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: gh release create "$GITHUB_REF_NAME" --title "$GITHUB_REF_NAME" --notes-file release-notes.md --verify-tag