fix(cli): move api-block assertions into a real .ts file

skipLibCheck exempts .d.ts contents from being checked, so assertions
written inside wrnexus.generated.d.ts were never evaluated by tsc.
Emit them into wrnexus.generated.api-checks.ts instead, referencing
the WRNexusGenerated namespace's helper types (which stay in the
.d.ts). Track the new generated file in check:generated-types.

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

scripts/check-generated-types.ts

@@ -8,6 +8,7 @@ const scratchParent = join(root, ".wrnexus-type-check");
 const scratch = mkdtempSync(`${scratchParent}-`);
 const generated = [
   join("app", "types", "wrnexus.generated.d.ts"),
+  join("app", "types", "wrnexus.generated.api-checks.ts"),
   join("app", "types", "wrnexus.plugins.generated.d.ts"),
 ];