feat(build): generate keyed view commands

Add lower-aware generated append/prepend/replace helpers for keyed slots, move the v0 keyed todo example off the facade extension trait, and keep beginner examples from importing lower-level render shortcuts.

req: dx/006

req: codegen/002

req: public_api/003

req: examples/003

examples/v0/src/lib.rs

@@ -5,7 +5,7 @@ pub mod ui {}
 mod tests {
     use super::ui::{auth, counter, notifications, page_swap, todos, wizard};
     use hemplate::Hemplate;
-    use slhx::{push, Effect, IntoEffect, NavigateMode, Payload, RenderKeyedSlotExt};
+    use slhx::{push, Effect, IntoEffect, NavigateMode, Payload};
     use slhx_test::inspect;
 
     #[derive(Clone, Debug)]
@@ -77,7 +77,8 @@ mod tests {
     fn todos_append_keyed_rows_from_form_input() {
         fn add_todo(input: TodoInput) -> impl IntoEffect {
             let todo = Todo { id: 7, title: input.title };
-            todos::slots::todo_row.append(
+            todos::append(
+                todos::slots::todo_row,
                 todo.id.to_string(),
                 &TodoRow { title: todo.title },
             )