feat(axum): add concise interaction request dispatch

Wrap extracted interaction forms in an InteractionRequest with a concise dispatch path, add a handlers() helper, and move canonical examples off direct HandlerRegistry/InteractionForm plumbing.

req: axum_integration/003

req: ceremony/001

req: dx/003

req: examples/003

examples/kanban/src/main.rs

@@ -5,7 +5,10 @@ use axum::Router;
 use futures_util::{stream, StreamExt};
 use hemplate::Hemplate;
 use slhx::{IntoEffect, RenderSlotExt, SafeHtml};
-use slhx_axum::{runtime_js, sse, DispatchRejection, EffectResponse, HandlerRegistry, InteractionForm, PageRequest};
+use slhx_axum::{
+    handlers, runtime_js, sse, DispatchRegistry, DispatchRejection, EffectResponse,
+    InteractionRequest, PageRequest,
+};
 use slhx_kanban_example::ui::{self, board as board_ui};
 use slhx_kanban_example::ui::board::{forms, handles, slots};
 use slhx_kanban_example::ui::board_card::handles as card_handles;
@@ -127,9 +130,9 @@ async fn runtime() -> impl IntoResponse {
 
 async fn interact(
     State(state): State<Arc<AppState>>,
-    form: InteractionForm,
+    request: InteractionRequest,
 ) -> Result<EffectResponse, DispatchRejection> {
-    registry(state).dispatch(form)
+    request.dispatch(registry(state))
 }
 
 // req: push/001 req: push/003 req: examples/001
@@ -148,8 +151,8 @@ async fn events(Query(params): Query<BTreeMap<String, String>>) -> impl IntoResp
     sse(batches)
 }
 
-fn registry(state: Arc<AppState>) -> HandlerRegistry {
-    HandlerRegistry::new(ui::BUILD_FINGERPRINT)
+fn registry(state: Arc<AppState>) -> impl DispatchRegistry {
+    handlers(ui::BUILD_FINGERPRINT)
         .register_handle(handles::create_card, {
             let state = state.clone();
             move |form| {