Adds 3 integration tests for Sort operations: - Test 3: Sort(IEnumerable<IContent>) reorders children correctly - Test 4: Sort(IEnumerable<int>) reorders children by ID correctly - Test 5: Sort fires Sorting and Sorted notifications in sequence 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>