feat(build): accept domain ids on keyed targets

Let generated string-keyed targets accept displayable domain ids directly, removing caller-side to_string noise from keyed partial append/replace flows.

req: codegen/002

req: dx/006

examples/v0/src/lib.rs

@@ -77,7 +77,7 @@ 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::targets::todo_row.append(todo.id.to_string(), &TodoRow { title: todo.title })
+            todos::targets::todo_row.append(todo.id, &TodoRow { title: todo.title })
         }
 
         let effect = inspect(add_todo(TodoInput { title: "Ship v0".into() }));