feat: replace the ssr/client data blocks with apis blocks

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

examples/basic-app/app/pages/api-block-demo.wrn

@@ -3,8 +3,8 @@ page ApiBlockDemo {
   state found = ""
   state failed = ""
 
-  client {
-    api searchDirectory POST /api/directory {
+  apis {
+    searchDirectory POST /api/directory {
       request {
         body {
           name?: string