fix files directory handling: use internal storage and add exception handling

- Use internal files dir instead of external (fixes scoped storage permissions)
- Pass files directory from Android context via JNI instead of hardcoding
- Add exception handling in ScanAppsDirectory to prevent crashes on permission errors
- Use std::error_code overload of fs::exists() to avoid throwing on access denial

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/main/cpp/apps/app_manager.cpp

@@ -585,13 +585,20 @@ bool AppManager::DownloadFile(const std::string& url, const std::string& dest_pa
 void AppManager::ScanAppsDirectory() {
     std::string apps_dir = m_data_root + "/apps";
 
+    try {
         if (!fs::exists(apps_dir)) {
             return;
         }
+    } catch (const std::exception& e) {
+        LOG_ERROR("Cannot access apps directory: %s", e.what());
+        return;
+    }
 
     LOG_INFO("Scanning apps directory: %s", apps_dir.c_str());
 
+    try {
         for (const auto& entry : fs::directory_iterator(apps_dir)) {
+            try {
                 if (!entry.is_directory()) {
                     continue;
                 }
@@ -610,13 +617,18 @@ void AppManager::ScanAppsDirectory() {
                 std::string actual_manifest;
                 std::string app_base_path;
 
-        if (fs::exists(manifest_path)) {
+                // Use error_code overload to avoid exceptions on permission errors
+                std::error_code ec;
+                if (fs::exists(manifest_path, ec) && !ec) {
                     actual_manifest = manifest_path;
                     app_base_path = entry.path().string();
-        } else if (fs::exists(manifest_path_pkg)) {
+                } else if (fs::exists(manifest_path_pkg, ec) && !ec) {
                     actual_manifest = manifest_path_pkg;
                     app_base_path = entry.path().string() + "/package";
                 } else {
+                    if (ec) {
+                        LOG_WARN("Cannot access %s: %s", package_id.c_str(), ec.message().c_str());
+                    }
                     continue;
                 }
 
@@ -626,7 +638,6 @@ void AppManager::ScanAppsDirectory() {
                     continue;
                 }
 
-        try {
                 json j;
                 mf >> j;
 
@@ -657,9 +668,12 @@ void AppManager::ScanAppsDirectory() {
                 LOG_INFO("Discovered app: %s (%s)", app.name.c_str(), app.package_id.c_str());
 
             } catch (const std::exception& e) {
-            LOG_WARN("Failed to parse manifest for %s: %s", package_id.c_str(), e.what());
+                LOG_WARN("Error processing app entry: %s", e.what());
             }
         }
+    } catch (const std::exception& e) {
+        LOG_ERROR("Error scanning apps directory: %s", e.what());
+    }
 }
 
 void AppManager::LoadInstalledApps() {

src/main/cpp/kernel.cpp

@@ -27,6 +27,9 @@
 #include <mosis/sandbox/crypto_api.h>
 #include <mosis/sandbox/virtual_fs.h>
 
+// External function to get files directory from JNI
+extern const std::string& GetFilesDir();
+
 // Global state for Lua access
 static Rml::Context* g_context = nullptr;
 static Rml::ElementDocument* g_document = nullptr;
@@ -500,9 +503,15 @@ void Kernel::main_loop()
     Logger::Log("RmlUi Lua bindings initialized");
 
     // Initialize app management system
-    // TODO: Get data root from Android context (for now use a placeholder)
-    std::string data_root = "/data/data/com.omixlab.mosis/files";
+    // Get files directory from Android context (set via JNI)
+    std::string data_root = GetFilesDir();
+    if (data_root.empty()) {
+        // Fallback if not set (shouldn't happen in normal operation)
+        data_root = "/data/data/com.omixlab.mosis/files";
+        Logger::Log("Warning: Files directory not set, using fallback");
+    }
     g_data_root = data_root;  // Store for sandbox switching
+    Logger::Log("Using data root: " + data_root);
     m_app_manager = std::make_unique<mosis::AppManager>(data_root);
     m_update_service = std::make_unique<mosis::UpdateService>(
         m_app_manager.get(), "https://portal.mosis.dev/api/v1");

src/main/cpp/mosis-service.cpp

@@ -84,3 +84,21 @@ Java_com_omixlab_mosis_NativeService_setAssetManager(JNIEnv *env, jobject thiz,
 {
     AssetsManager::Init(AAssetManager_fromJava(env, asset_manager));
 }
+
+// Global storage for files directory path
+static std::string g_files_dir;
+
+extern "C"
+JNIEXPORT void JNICALL
+Java_com_omixlab_mosis_NativeService_setFilesDir(JNIEnv *env, jobject thiz,
+    jstring files_dir)
+{
+    const char* path = env->GetStringUTFChars(files_dir, nullptr);
+    g_files_dir = path;
+    env->ReleaseStringUTFChars(files_dir, path);
+    LOG_INFO("Files directory set to: %s", g_files_dir.c_str());
+}
+
+const std::string& GetFilesDir() {
+    return g_files_dir;
+}

src/main/java/com/omixlab/mosis/NativeService.kt

@@ -19,6 +19,7 @@ class NativeService : Service() {
     }
     external fun getBinderNative(): IBinder
     external fun setAssetManager(assetManager: AssetManager)
+    external fun setFilesDir(filesDir: String)
 
     override fun onBind(intent: Intent): IBinder {
         return getBinderNative()
@@ -27,6 +28,9 @@ class NativeService : Service() {
     override fun onCreate() {
         super.onCreate()
         setAssetManager(assets)
+        // Use internal files dir - more reliable access in service processes
+        // For debugging, use: adb shell run-as com.omixlab.mosis ls files/
+        setFilesDir(filesDir.absolutePath)
     }
 
     override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {