debug(format): print viewport policy canonical output

scripts/format.mjs

@@ -120,6 +120,15 @@ export async function formatAdoptedFiles(root, mode) {
   }
 
   const changed = files.filter(({ source, formatted }) => source !== formatted);
+  if (mode === '--check') {
+    const target = changed.find(
+      ({ name }) => name === 'src/voice/realtimeViewportPolicy.test.mjs',
+    );
+    if (target)
+      console.error(
+        `FORMAT_EXPECTED BEGIN\n${target.formatted}FORMAT_EXPECTED END`,
+      );
+  }
   if (mode === '--write') {
     for (const { file, formatted } of changed) await writeFile(file, formatted);
   }