feat(syntax): parse sectioned api blocks

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

packages/syntax/src/parser.ts

@@ -1,4 +1,5 @@
 import { WRN_RUNTIME_TARGETS } from "./spec.ts";
+import { parseApiSections, hasRequestSection, type ApiSections } from "./api-sections.ts";
 
 /**
  * Recursive-descent parser for `.wrn`, producing a small AST.
@@ -148,7 +149,10 @@ export interface DataApiBlock {
   name: string;
   method: string;
   path: string;
+  /** Legacy bare body. Empty string when `sections` is set. */
   body: string;
+  /** Present only for the sectioned, typed form. */
+  sections?: ApiSections;
 }
 
 export interface ModeFunctionsBlock {
@@ -696,7 +700,20 @@ export function parse(source: string): PageAst {
                 const method = expect("ident").value.toUpperCase();
                 const path = lx.readPath();
                 const body = lx.readBalancedBraces();
-                dataApis.push({ mode, name, method, path, body });
+                const sections = parseApiSections(body);
+                if (sections && mode !== "client" && hasRequestSection(body)) {
+                  throw new ParseError(
+                    `An ssr api block cannot declare "request": there is no caller at render time to supply it. Use a client block, or a server function.`,
+                  );
+                }
+                dataApis.push({
+                  mode,
+                  name,
+                  method,
+                  path,
+                  body: sections ? "" : body,
+                  ...(sections ? { sections } : {}),
+                });
                 break;
               }
               case "functions": {