Fix update installer handoff

[enaboapps]

Summary

• add a native Windows update launcher helper that uses ShellExecuteExW with runas and confirms an installer process handle
• replace the app-triggered updater handoff so Switchify PC quits only after confirmed launcher success
• add bounded update-install diagnostics and renderer messages for launcher/UAC failures
• package, sign, smoke, and verify the new helper
• require isAdminRightsRequired: true in generated updater metadata

Closes #267.

Validation

• npm test -- src/main/updates/update-installer-launcher.test.ts src/main/updates/update-install-diagnostics.test.ts src/main/updates/update-service.test.ts src/main/updates/update-ipc.test.ts src/renderer/updates.test.ts src/main/sign-win-artifacts.test.ts src/main/package-win-after-pack.test.ts
• npm run native:build
• npm run native:smoke-update-launcher
• npm test
• npm run typecheck
• npm run build
• npm run package:win
• npm run package:win:verify-uiaccess
• npm run package:win:verify-updater-metadata
• rg -n "quitAndInstall" src confirms production code has no usage