test: restore executed and real-tsc coverage lost when the old api-block tests were deleted

Fix round 1: the deleted api-block-*.test.ts files were not fully superseded
by the apis-* siblings as claimed. Ports back, using apis {} fixtures:
- brace-inside-a-string-literal response-section scanner regression test
- type erasure of response/error bodies before browser emission
- client-side response-error-not-swallowed / transport-failure-fallback,
  executed via dynamic import of a generated browser module
- the full SSR execution suite: response payload binding, error section
  status/message/data binding, {#each} failure propagation, all executed
  via dynamic import + a real load/api call chain (not string checks)
- the four real-tsc enforcement tests (matching/wrong-type/extra-field/
  missing-field), plus the B1 cross-page collision guard and the B6
  export-for-noUnusedLocals guard

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

packages/syntax/test/apis-block.test.ts

@@ -97,3 +97,27 @@ test("an explicit empty response section is accepted, unlike a bare body", () =>
   expect(block.name).toBe("empty");
   expect(block.sections?.response.trim()).toBe("");
 });
+
+test("a brace inside a string literal in the response body does not truncate the section", () => {
+  const ast = parse(
+    page(`    searchUsers POST /api/users {
+      request {
+        body {
+          name?: string
+        }
+      }
+
+      response {
+        return "a } weird string"
+      }
+
+      error {
+        return []
+      }
+    }`),
+  );
+
+  const block = ast.dataApis[0]!;
+  expect(block.sections?.response.trim()).toBe('return "a } weird string"');
+  expect(block.sections?.error.trim()).toBe("return []");
+});