[Feature] Add unit tests for setNewArch command file manipulation logic

[ConnorQi01]

Summary

The setNewArch command (src/extension/commands/setNewArch.ts) modifies ios/Podfile and android/gradle.properties to toggle React Native New Architecture. This logic has no unit tests, leaving the file-parsing and write-back paths unverified.

Why this is useful

Similar commands with non-trivial file manipulation — enableHermes, installExpoGoApplication, prebuild, configEASBuild — all have unit tests. Adding tests for setNewArch closes a consistency gap and guards against regressions when the New Architecture flags or file formats change.

Suggested scope

• Add test/extension/commands/setNewArch.test.ts following the proxyquire/sinon pattern used by adjacent tests
• Cover: Android path (gradle.properties has existing newArchEnabled entry vs. missing entry), iOS path (Podfile includes the disable line vs. does not), and user-cancellation (QuickPick returns undefined)
• Fix the typo in InternalErrorCode: FaiedToSetNewArch → FailedToSetNewArch (src/common/error/internalErrorCode.ts:40)

Evidence

• src/extension/commands/setNewArch.ts — 87 lines, no corresponding test file under test/extension/commands/
• src/common/error/internalErrorCode.ts:40 — FaiedToSetNewArch = 135 (typo)
• Comparable test: test/extension/commands/enableHermes.test.ts uses temp-dir + proxyquire pattern that applies directly here

Validation

• npm test passes with the new test file included
• Both Android and iOS branches exercised in isolation without touching real project files