fix(macos-test-app): bump react-native core to 0.81.6 for the macos 0.81.8 peer

react-native-macos-init failed to install react-native-macos@0.81.8 because it
peer-pins react-native 0.81.6 exactly, while REACT_NATIVE_VERSION was still
0.81.5 (the peer for the previous 0.81.1). Bump core to 0.81.6 so the two align.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011PM3HdJVbivXpzc2MQJV9T

Author: claude

scripts/init-macos-test-app.ts

@@ -4,7 +4,9 @@ import fs from "node:fs";
 import path from "node:path";
 import { readPackage } from "read-pkg";
 
-const REACT_NATIVE_VERSION = "0.81.5";
+// react-native-macos peer-pins an exact react-native core version
+// (react-native-macos 0.81.8 -> react-native 0.81.6); keep these two in lockstep.
+const REACT_NATIVE_VERSION = "0.81.6";
 const REACT_NATIVE_MACOS_VERSION = "0.81.8";
 const REACT_VERSION = "^19.1.4";