feat(axum): add interaction registry alias

Add an interactions()/on() registration path and move canonical examples off explicit register_handle naming while keeping low-level registry types available underneath.

req: axum_integration/003

req: ceremony/001

req: dx/003

req: examples/003

slhx-axum/tests/response.rs

@@ -2,7 +2,7 @@ use axum::http::{header, HeaderMap};
 use axum::response::IntoResponse;
 use scraper::{Html, Selector};
 use slhx_axum::{
-    handlers, runtime_js, DispatchRejection, EffectResponse, HandlerRegistry, InteractionForm,
+    interactions, runtime_js, DispatchRejection, EffectResponse, HandlerRegistry, InteractionForm,
     InteractionFormRejection, InteractionRequest, PageMode, PageRequest, PageResponse,
     SLHX_CONTENT_TYPE, SLHX_FINGERPRINT_HEADER, SLHX_PARTIAL_HEADER, SLHX_RUNTIME_CONTENT_TYPE,
     SLHX_TITLE_HEADER,
@@ -148,7 +148,7 @@ fn interaction_request_dispatches_with_concise_handlers_helper() {
         Vec::new(),
     ));
     let response = request
-        .dispatch(handlers(BuildFingerprint(4)).register_handle(Handle::<()>::new(7), |_| {
+        .dispatch(interactions(BuildFingerprint(4)).on(Handle::<()>::new(7), |_| {
             Slot::<String>::new(3).text("ok")
         }))
         .unwrap();