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

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

packages/syntax/test/removed-mode-blocks.test.ts

@@ -0,0 +1,33 @@
+import { expect, test } from "bun:test";
+import { parse } from "../src/index.ts";
+
+test("an ssr data block is rejected and names the replacement", () => {
+  expect(() =>
+    parse(`page P {
+  ssr { api x GET /api/x { return users } }
+  view { <main>x</main> }
+}
+`),
+  ).toThrow(/apis/);
+});
+
+test("a client data block is rejected and names the replacement", () => {
+  expect(() =>
+    parse(`page P {
+  client { api x GET /api/x { return users } }
+  view { <main>x</main> }
+}
+`),
+  ).toThrow(/apis/);
+});
+
+test("client state is unaffected", () => {
+  // Different construct sharing the keyword. It must keep working.
+  const ast = parse(`page P {
+  client state { count = 0 }
+  view { <main>x</main> }
+}
+`);
+
+  expect(ast.states.some((state) => state.name === "count")).toBe(true);
+});