fix(stage2): launch the app under test in English whatever the device language

[dadachi]

Closes #159

Stage 2 waits for English UI text ("Welcome to", button labels) but the generated apps follow the device language, so a simulator set to Japanese failed Stage 2 on its first step.

Changes

• iOS — Stage 1's install/launch (src/validation/launch.ts) now runs xcrun simctl launch booted <bundle> -AppleLanguages "(en)" -AppleLocale en_US.
• Android — after install, before the monkey launch: adb shell cmd locale set-app-locales <pkg> --locales en-US (Android 13 / API 33+). If it fails (older Android), the launch still goes ahead and a warning (LaunchResult.warnings) is traced: the app then follows the device language.
• Stage 2 foreground / springboard relaunch — MobileClient.launchApp(pkg, locale) passes locale: "en-US" to mobile-mcp's mobile_launch_app (0.0.54 supports it: -AppleLanguages/-AppleLocale on iOS simulators through mobilecli, set-app-locales on Android), so the retry path is English too.
• Non-English UI detection — when a wait_for_text / tap_text step fails and the screen shows non-Latin text, the Stage 2 error reads environment: the app's UI is not in English (the screen shows "Orange Baton へようこそ") although the agent launched it in English (...); ... Set the simulator's language to English and re-run. (<original step error>). Deliberately simple: Latin-script languages (French, German) still surface as a plain step failure.
• installAndLaunch / selectAdbTarget take an injectable exec layer (LaunchExec) so the commands are unit-tested without simctl/adb.
• README: one sentence on the English launch under NATIVEAPPTEMPLATE_VISUAL=2.

Tests

• iOS launch args, Android set-app-locales ordering (after install, before monkey; emulator picked over a phone), Android < 13 fallback warning — via a recording exec.
• The existing springboard-relaunch test now asserts both launches ask for en-US.
• Stage 2 on a fake mobile-mcp screen showing Orange Baton へようこそ → environment: error; an English screen keeps the plain error.
• Each new assertion was seen red by reverting its piece of the fix (5 failures), then green. npm run ci: 192 pass.

Real-device check (no paid run)

Using the already-built Orange Baton app:

• iPhone 17 Pro simulator (iOS 26.2) switched to AppleLanguages (ja-JP, en-US) / ja_JP: plain simctl launch → Japanese UI; installAndLaunch from this branch → "Welcome to Orange Baton" / "Start" / "Support Website".
• mobile-mcp 0.0.54 mobile_launch_app on the same Japanese simulator: without locale → Orange Batonへようこそ | はじめる; with locale: "en-US" → Welcome to Orange Baton | Start (both attempts).
• Android emulator (API 37) with device locale ja-JP: plain launch → Orange Batonへようこそ / はじめる; installAndLaunch from this branch → English, get-app-locales = [en-US].
• Simulator restored to en-US, ja-JP / en_US and left booted; emulator restored to en-US.

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https://claude.ai/code/session_01UZJxUoubntzu7Ec7DPVfAr