Fix workout_app service tests on non-Android hosts

Pre-existing failures unrelated to the manual-workout feature, exposed once the
pre-push flutter gate started running the Dart suite:

- http_server_service / sync_service: getExternalStorageDirectory() throws
  UnsupportedError (an Error, not an Exception) on non-Android platforms, so the
  `on Exception` fallbacks didn't catch it and it escaped, failing start() and
  writeWorkoutResult(). External storage is Android-only, so guard the call with
  Platform.isAndroid instead of trying to catch a platform Error.
- sync_service_test: the "updates HttpServerService" assertion expected compact
  JSON ("workout_type":"A") but the payload is pretty-printed
  ("workout_type": "A"); fixed the expectation to match.

Full workout_app suite (191 tests) now passes on this host.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PM3auNTifaVgcXWDizZrjH

stronglift_replacement/workout_app/lib/services/http_server_service.dart

@@ -67,11 +67,16 @@ class HttpServerService {
   /// HTTP endpoint is populated even before the next workout is completed.
   Future<void> _loadFromDisk() async {
     final candidates = <String>[kSyncFilePath];
-    try {
-      final dir = await getExternalStorageDirectory();
-      if (dir != null) candidates.add('${dir.path}/workout_result.json');
-    } on Exception {
-      // Ignore; the /sdcard path is tried first.
+    // External storage is Android-only; getExternalStorageDirectory() throws an
+    // UnsupportedError (not an Exception) on other platforms (desktop / test
+    // host), so guard the call rather than trying to catch it.
+    if (Platform.isAndroid) {
+      try {
+        final dir = await getExternalStorageDirectory();
+        if (dir != null) candidates.add('${dir.path}/workout_result.json');
+      } on Exception {
+        // Ignore; the /sdcard path is tried first.
+      }
     }
     for (final path in candidates) {
       final file = File(path);

stronglift_replacement/workout_app/lib/services/sync_service.dart

@@ -29,15 +29,19 @@ class SyncService {
       // Fallback: app-specific external directory (still ADB accessible).
     }
 
-    try {
-      final dir = await getExternalStorageDirectory();
-      if (dir != null) {
-        final file = File('${dir.path}/workout_result.json');
-        await file.writeAsString(json);
-        return SyncResult(success: true, path: file.path);
+    // External storage is Android-only; getExternalStorageDirectory() throws an
+    // UnsupportedError (not an Exception) on other platforms, so guard the call.
+    if (Platform.isAndroid) {
+      try {
+        final dir = await getExternalStorageDirectory();
+        if (dir != null) {
+          final file = File('${dir.path}/workout_result.json');
+          await file.writeAsString(json);
+          return SyncResult(success: true, path: file.path);
+        }
+      } on Exception {
+        // Fallback failed.
       }
-    } on Exception {
-      // Fallback failed.
     }
 
     return const SyncResult(

stronglift_replacement/workout_app/test/services/sync_service_test.dart

@@ -63,7 +63,7 @@ void main() {
       // The HTTP server must be updated regardless of file write success.
       expect(
         HttpServerService.instance.latestWorkout,
-        contains('"workout_type":"A"'),
+        contains('"workout_type": "A"'),
       );
     });