docs(kanban): use generated keyed commands

Keep the north-star kanban sketches aligned with the generated lower-aware append/replace helpers instead of teaching keyed slot extension methods.

req: dx/006

req: codegen/002

examples/kanban.md

@@ -92,7 +92,7 @@ slhx reads this from hemplate Surface facts and generates scoped typed resources
 ```rust
 use ui::board::{forms, slots};
 
-slots::card.replace(card.id, CardView::from(card));
+ui::board::replace(slots::card, card.id, &CardView::from(card));
 forms::create_card.clear("title");
 ui::render(&BoardView::from(board));
 ```
@@ -135,7 +135,7 @@ pub fn create_card(
     app.board.update(|board| board.insert_card(form.column, card.clone()));
 
     (
-        slots::card.append(card.id, &CardView::from(card)),
+        ui::board::append(slots::card, card.id, &CardView::from(card)),
         forms::create_card.clear("title"),
         // slhx-sync: queue atomic board state diff for sync
         SyncEffect::send_patch(atoms::board, Patch::insert_card(form.column, card)),
@@ -233,7 +233,7 @@ pub fn apply_board_patch(
             Effect::broadcast(
                 Channel::Board(app.board.id()),
                 Effect::batch(changed_cards.into_iter().map(|c|
-                    slots::card.replace(c.id, &CardView::from(c))
+                    ui::board::replace(slots::card, c.id, &CardView::from(c))
                 )),
             ),
         )),
@@ -255,7 +255,7 @@ Server-authoritative on conflict. No Redux sagas. No React Query cache fades.
 ```rust
 #[slhx_sync::presence]
 pub fn user_joined(user: UserPresence) -> impl IntoEffect {
-    slots::presence_user.append(user.id, &PresenceBadge::from(user))
+    ui::board::append(slots::presence_user, user.id, &PresenceBadge::from(user))
 }
 ```