Package-level declarations

Annotations for declaring RPC services (@KsService, @KsMethod), typed error bindings (@KsError), notification semantics (@KsNotification), method-level timeouts (@KsTimeout), and per-call context propagation (@KsContext). Also includes the @KsMethodMetadata meta-annotation for extending the compiler plugin with custom sibling annotations.

Contains @KsIntrospectable, the opt-in annotation that triggers compiler generation of introspection metadata for a @KsService.