Android: hardware step-counter bridge for step-sync mods

love.system.syncHealthSteps() now exists on Android, matching the iOS
Health bridge merged in #452 and using the same JNI route as the SAF
picker (wrap_System.cpp -> System.cpp -> common/android.cpp ->
GameActivity over JNI):

- GameActivity.syncHealthSteps: one-shot read of the hardware
  TYPE_STEP_COUNTER sensor (cumulative since boot, counted by the OS
  whether or not any app runs). The reading is anchored in
  SharedPreferences so a walk is never credited twice; a reading below
  the anchor means the phone rebooted, which re-anchors without
  crediting. Deltas (50k clamp) merge into steps_pending.json in the
  save identity dir - the same contract as the iOS GRHealthBridge, so
  the Pokewalker mod works unchanged on both platforms.
- ACTIVITY_RECOGNITION declared in the app manifest (Android 10+
  runtime prompt on first sync; granted -> the sensor read runs
  immediately via onRequestPermissionsResult). The build script's
  permission trim leaves it alone.
- Nothing in the base game calls the new seam; without a consumer mod
  the only cost is one dormant manifest permission.
- build_android.sh: shadow-build from a space-free temp dir when the
  checkout path contains spaces - ndk-build is GNU make underneath and
  cannot cope with paths like "xCode Projects".
- mobile/ANDROID.md: step-bridge dev notes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

mobile/android/love/src/jni/love/src/common/android.cpp

@@ -219,6 +219,18 @@ bool showCreateDocument(const char *suggestedName)
 	return result;
 }
 
+bool syncHealthSteps()
+{
+	JNIEnv *env = (JNIEnv*) SDL_AndroidGetJNIEnv();
+	jclass activity = env->FindClass("org/love2d/android/GameActivity");
+
+	jmethodID method = env->GetStaticMethodID(activity, "syncHealthSteps", "()Z");
+	jboolean result = env->CallStaticBooleanMethod(activity, method);
+
+	env->DeleteLocalRef(activity);
+	return result;
+}
+
 /*
  * Helper functions for the filesystem module
  */

mobile/android/love/src/jni/love/src/common/android.h

@@ -74,6 +74,13 @@ bool showFilePicker(const char *destFilename = nullptr);
  **/
 bool showCreateDocument(const char *suggestedName = nullptr);
 
+/**
+ * Pokéwalker step bridge: asks GameActivity to read the hardware step
+ * counter and stage steps_pending.json in the save identity dir (see
+ * GameActivity.syncHealthSteps). Returns whether a sync could start.
+ */
+bool syncHealthSteps();
+
 /*
  * Helper functions for the filesystem module
  */

mobile/android/love/src/jni/love/src/modules/system/System.cpp

@@ -212,6 +212,15 @@ bool System::createFile(const char *suggestedName) const
 #endif
 }
 
+bool System::syncHealthSteps() const
+{
+#ifdef LOVE_ANDROID
+	return love::android::syncHealthSteps();
+#else
+	return false;
+#endif
+}
+
 bool System::hasBackgroundMusic() const
 {
 #if defined(LOVE_ANDROID)

mobile/android/love/src/jni/love/src/modules/system/System.h

@@ -127,6 +127,12 @@ public:
 	 **/
 	virtual bool createFile(const char *suggestedName = nullptr) const;
 
+	/**
+	 * Pokéwalker: stage pending real-world steps (steps_pending.json in the
+	 * save dir) from the platform step source. Android-only; false elsewhere.
+	 */
+	virtual bool syncHealthSteps() const;
+
 	/**
 	 * Gets if the user is playing music on background.
 	 * Throws an exception on unsupported platforms.

mobile/android/love/src/jni/love/src/modules/system/wrap_System.cpp

@@ -109,6 +109,12 @@ int w_createFile(lua_State *L)
 	return 1;
 }
 
+int w_syncHealthSteps(lua_State *L)
+{
+	luax_pushboolean(L, instance()->syncHealthSteps());
+	return 1;
+}
+
 int w_hasBackgroundMusic(lua_State *L)
 {
 	lua_pushboolean(L, instance()->hasBackgroundMusic());
@@ -126,6 +132,7 @@ static const luaL_Reg functions[] =
 	{ "vibrate", w_vibrate },
 	{ "pickFile", w_pickFile },
 	{ "createFile", w_createFile },
+	{ "syncHealthSteps", w_syncHealthSteps },
 	{ "hasBackgroundMusic", w_hasBackgroundMusic },
 	{ 0, 0 }
 };