feat(axum): register checked handles

Add HandlerRegistry::register_handle for generated Handle<T> values and migrate examples away from passing raw numeric handle ids at registration sites.

req: ceremony/004

req: public_api/001

slhx-axum/tests/response.rs

@@ -6,7 +6,7 @@ use slhx_axum::{
     InteractionFormRejection, PageMode, PageRequest, PageResponse, SLHX_CONTENT_TYPE,
     SLHX_FINGERPRINT_HEADER, SLHX_PARTIAL_HEADER, SLHX_RUNTIME_CONTENT_TYPE, SLHX_TITLE_HEADER,
 };
-use slhx_core::{push, BuildFingerprint, Slot};
+use slhx_core::{push, BuildFingerprint, Handle, Slot};
 
 fn selector(value: &str) -> Selector {
     Selector::parse(value).expect("test selector parses")
@@ -100,14 +100,16 @@ fn interaction_form_preserves_hidden_csrf_fields_for_extractors() {
 }
 
 #[test]
-fn handler_registry_dispatches_by_numeric_handle_id() {
+fn handler_registry_dispatches_by_checked_handle() {
+    // req: ceremony/004 req: public_api/001
     let title = Slot::<String>::new(7);
-    let registry = HandlerRegistry::new(BuildFingerprint(123)).register(42, move |form| {
+    let create = Handle::<()>::new(42);
+    let registry = HandlerRegistry::new(BuildFingerprint(123)).register_handle(create, move |form| {
         title.text(form.value("title").unwrap_or(""))
     });
 
     let response = registry
-        .dispatch(InteractionForm::new(42, [("title".into(), "Hello".into())]))
+        .dispatch(InteractionForm::new(create.id().id, [("title".into(), "Hello".into())]))
         .unwrap();
 
     assert_eq!(response.batch.fingerprint, BuildFingerprint(123));