fix(eas): use 'bun x' instead of 'bunx' in custom build configs

The latest EAS Android build image no longer ships the bunx shim,
so 'bunx expo prebuild' fails with exit 127 (command not found).
'bun x' is bun's built-in equivalent and only requires the bun
binary itself, which the image provides.

Claude-Session: https://claude.ai/code/session_01GVcoCm9p5pLBXS9v8jDkHp

.eas/build/android-production-apk.yml

@@ -13,7 +13,7 @@ build:
 
     - run:
         name: Prebuild (Android, bun)
-        command: bunx expo prebuild --platform android --no-install
+        command: bun x expo prebuild --platform android --no-install
 
     - eas/configure_android_version
     - eas/inject_android_credentials

.eas/build/android-production-tv.yml

@@ -15,7 +15,7 @@ build:
     # EXPO_TV=1 comes from the profile env, so prebuild targets Android TV.
     - run:
         name: Prebuild (Android TV, bun)
-        command: bunx expo prebuild --platform android --no-install
+        command: bun x expo prebuild --platform android --no-install
 
     - eas/configure_android_version
     - eas/inject_android_credentials

.eas/build/android-production.yml

@@ -18,10 +18,10 @@ build:
         command: bun install --frozen-lockfile
 
     # android/ is gitignored, so generate native code fresh. --no-install
-    # because deps are already installed above; bunx keeps it on bun.
+    # because deps are already installed above; bun x keeps it on bun.
     - run:
         name: Prebuild (Android, bun)
-        command: bunx expo prebuild --platform android --no-install
+        command: bun x expo prebuild --platform android --no-install
 
     # Applies the EAS-resolved remote versionCode/versionName (autoIncrement
     # in eas.json) into the freshly prebuilt android/ project.

.eas/build/ios-production.yml

@@ -26,7 +26,7 @@ build:
     # skips JS + pod install; we install pods explicitly below with bun deps.
     - run:
         name: Prebuild (iOS/tvOS, bun)
-        command: bunx expo prebuild --platform ios --no-install
+        command: bun x expo prebuild --platform ios --no-install
 
     - run:
         name: Install CocoaPods