fix: improve error handling and compatibility

Add directory existence check in CsvToDsConverter::dsToCsv. Allow null GAME align callback in TranscriptionPipeline. Fix FileIOProvider ownership to support test injection. Fix signed/unsigned comparison warning in Slicer. Adapt TestCsvToDsConverter to static DsDocument::loadFile API.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

Author: wolfgitpr

src/domain/src/CsvToDsConverter.cpp

@@ -247,6 +247,10 @@ bool CsvToDsConverter::dsToCsv(const QString &dsDir,
                                 const QString &csvPath,
                                 QString &error) {
     QDir dir(dsDir);
+    if (!dir.exists()) {
+        error = QStringLiteral("Directory does not exist: ") + dsDir;
+        return false;
+    }
     const QFileInfoList entries = dir.entryInfoList(
         {QStringLiteral("*.ds")}, QDir::Files, QDir::Name);
 

src/domain/src/TranscriptionPipeline.cpp

@@ -241,8 +241,8 @@ bool TranscriptionPipeline::gameAlign(const Options &opts,
                                        ProgressCallback progress,
                                        QString &error) {
     if (!gameAlignCb) {
-        error = "GAME align callback is null";
-        return false;
+        // No callback — skip alignment, leave rows unchanged
+        return true;
     }
 
     const int total = static_cast<int>(rows.size());

src/framework/core/src/LocalFileIOProvider.cpp

@@ -98,19 +98,21 @@ Result<void> LocalFileIOProvider::copyFile(const QString &src, const QString &ds
     return Result<void>::Ok();
 }
 
-static std::unique_ptr<IFileIOProvider> s_provider =
+static std::unique_ptr<IFileIOProvider> s_ownedProvider =
     std::make_unique<LocalFileIOProvider>();
+static IFileIOProvider *s_activeProvider = s_ownedProvider.get();
 
 IFileIOProvider *fileIOProvider() {
-    return s_provider.get();
+    return s_activeProvider;
 }
 
 void setFileIOProvider(IFileIOProvider *provider) {
-    s_provider.reset(provider);
+    s_activeProvider = provider;
 }
 
 void resetFileIOProvider() {
-    s_provider = std::make_unique<LocalFileIOProvider>();
+    s_ownedProvider = std::make_unique<LocalFileIOProvider>();
+    s_activeProvider = s_ownedProvider.get();
 }
 
 }

src/infer/audio-util/src/Slicer.cpp

@@ -30,7 +30,7 @@ namespace AudioUtil
         output.reserve(output_size);
 
         for (size_t i = 0; i < output_size; ++i) {
-            const bool is_underflow = i * hop_length < frame_length / 2;
+            const bool is_underflow = static_cast<int>(i * hop_length) < frame_length / 2;
             const size_t start = is_underflow ? 0 : (i * hop_length - frame_length / 2);
             const size_t end = (std::min)(samples.size(), i * hop_length - frame_length / 2 + frame_length);
 
@@ -72,7 +72,7 @@ namespace AudioUtil
         output.reserve(output_size);
 
         for (size_t i = 0; i < output_size; ++i) {
-            const bool is_underflow = i * hop_length < frame_length / 2;
+            const bool is_underflow = static_cast<int>(i * hop_length) < frame_length / 2;
             const size_t start = is_underflow ? 0 : (i * hop_length - frame_length / 2);
             const size_t end = (std::min)(samples.size(), i * hop_length - frame_length / 2 + frame_length);
 

src/tests/domain/TestCsvToDsConverter.cpp

@@ -222,9 +222,10 @@ void TestCsvToDsConverter::testConvertFromMemory_dsContentVerification() {
     QString error;
     QVERIFY(CsvToDsConverter::convertFromMemory(rows, opts, mockF0, nullptr, error));
 
-    DsDocument doc;
     QString dsPath = tmpOut.path() + "/song1.ds";
-    QVERIFY(doc.loadFile(dsPath).ok());
+    auto loadResult = DsDocument::loadFile(dsPath);
+    QVERIFY(loadResult.ok());
+    DsDocument doc = std::move(loadResult.value());
     QVERIFY(!doc.sentences().empty());
 
     auto &s = doc.sentences()[0];