Add check to prevent releases from main branch

The release script now checks if it's being run from the main branch
and exits with an error message if so. This ensures releases are always
done from a dedicated release branch.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: oschwald

dev-bin/release.sh

@@ -2,6 +2,14 @@
 
 set -eu -o pipefail
 
+# Check that we're not on the main branch
+current_branch=$(git branch --show-current)
+if [ "$current_branch" = "main" ]; then
+    echo "Error: Releases should not be done directly on the main branch."
+    echo "Please create a release branch and run this script from there."
+    exit 1
+fi
+
 changelog=$(cat CHANGELOG.md)
 
 regex='