Improved type construction cycle handling in Go 1.26

The Go 1.26 update introduces improvements to the type checker's handling of type construction cycles, particularly for complex type declarations. This change doesn't affect most Go programmers' everyday experience but addresses subtle corner cases in the type system. The type checker now better manages internal data structures during compilation, specifically when encountering nested type definitions where types reference each other. These internal improvements establish a foundation for potential future enhancements to Go's static type system while maintaining backward compatibility.