Refactor: unify @SimpleBuilder and @SimpleBuilder.Template by making @SimpleBuilder a built-in template

[devin-ai-integration]

Context

@SimpleBuilder and the separate @SimpleBuilder.Template annotations are currently handled by two distinct discovery paths in BuilderProcessor:

• getElementsAnnotatedWith(SimpleBuilder.class)
• a loop over custom annotations whose type is meta-annotated with @SimpleBuilder.Template

SimpleBuilder is even explicitly excluded from the template scan in BuilderProcessor.shouldSkipAnnotation(...).

Idea

Instead of treating @SimpleBuilder as a special case, it could be made a built-in template annotation itself:

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.CLASS)
@SimpleBuilder.Template(options = @Options())
public @interface SimpleBuilder {
    // optional inline override of the template defaults
    Options options() default @Options();
}

@SimpleBuilder.Template already defines an Options options() member, so all properties that live on @SimpleBuilder can be expressed through Template.options.

Benefits

• A single discovery loop over all annotation types that are meta-annotated with @SimpleBuilder.Template (including @SimpleBuilder itself) would cover both built-in and custom templates.
• The processor code would no longer need the special SimpleBuilder branch, reducing duplication.
• It would make the inheritance model explicit: @SimpleBuilder (not @Inherited) is the default preset, while custom annotations can be @Inherited templates.

Open questions / caveats

• How are inline SimpleBuilder.options() overrides merged with the Template/options defaults from the meta-annotation?
• What happens to the @SimpleBuilder Javadoc and @Target? It must remain usable on types, while @Template is @Target(ANNOTATION_TYPE).
• Any changes here need dedicated tests to prove @SimpleBuilder still works standalone and custom templates still inherit correctly.