feat(slhx): prefer render methods for views

Move view rendering onto Slot::render and KeyedSlot append/prepend/replace extension methods, leaving explicit text/html methods for non-view escape hatches.

req: codegen/002

req: view/001

examples/kanban/src/lib.rs

@@ -27,7 +27,7 @@ mod tests {
     #[test]
     fn kanban_board_updates_generated_slot() {
         fn render_board() -> impl IntoEffect {
-            ui::board::slots::board.render_view(&empty_board())
+            ui::board::slots::board.render(&empty_board())
         }
 
         let effect = inspect(render_board());