fix error messaging

Author: OpenHypervideo

src/_shared/modules/Localization/locale/de.js

@@ -36,6 +36,7 @@ window.FrameTrail_L10n['de'] = {
 	"ErrorMissingSubtitleFile": "Untertitel-Datei nicht gefunden",
 	"ErrorNoAnnotationsIndexFile": "Annotations Index-Datei nicht gefunden",
 	"ErrorNoConfigFile": "Konfigurations-Datei nicht gefunden",
+	"ErrorBrowserFileProtocol": "Kein Zugriff auf den Datenordner. In Chrome oder Edge \u00f6ffnen f\u00fcr lokalen Ordnerzugriff, oder Seite mit PHP-Server aufrufen.",
 	"ErrorNoHypervideoIndexFile": "Hypervideo Index-Datei nicht gefunden",
 	"ErrorNoHypervideoJSONFile": "hypervideo.json Datei nicht gefunden",
 	"ErrorNoResourcesIndexFile": "Resources Index-Datei nicht gefunden",

src/_shared/modules/Localization/locale/en-US.js

@@ -36,6 +36,7 @@ window.FrameTrail_L10n['en-US'] = {
 	"ErrorMissingSubtitleFile": "Missing subtitle file",
 	"ErrorNoAnnotationsIndexFile": "No annotations index file",
 	"ErrorNoConfigFile": "No config file",
+	"ErrorBrowserFileProtocol": "No access to data folder. Open in Chrome or Edge for local folder access, or run page with PHP server.",
 	"ErrorNoHypervideoIndexFile": "No hypervideo index file",
 	"ErrorNoHypervideoJSONFile": "No hypervideo.json file",
 	"ErrorNoResourcesIndexFile": "No resources index file",

src/player/modules/PlayerLauncher/module.js

@@ -76,6 +76,15 @@
             return;
         }
 
+        if (storageMode === 'download' && window.location.protocol === 'file:' && FrameTrail.getState('config') === null) {
+            // Browser opened the file directly but doesn't support the File System Access API
+            // (e.g. Firefox, Safari). There is no way to load persistent data in this context.
+            // Only applies when no inline config was provided — examples with inline data work fine.
+            FrameTrail.module('InterfaceModal').hideLoadingScreen();
+            FrameTrail.module('InterfaceModal').showErrorMessage(labels['ErrorBrowserFileProtocol']);
+            return;
+        }
+
         // Sync login state now that storageMode is known.
         // UserManagement.isLoggedIn() ran at module-init time before storageMode
         // was set, so loggedIn may be stale (false) for local/download modes.