Add optional original, annotated and JSON frame outputs

include/output_writer.hpp

@@ -0,0 +1,20 @@
+#pragma once
+#include "frame_result.hpp"
+#include <filesystem>
+#include <string>
+namespace cms {
+struct OutputOptions {
+    bool original{},annotated{},results{};
+    std::filesystem::path directory;
+    bool enabled() const {return original||annotated||results;}
+};
+// Called by the inference worker; one matching filename stem per completed frame.
+class OutputWriter {
+public:
+    explicit OutputWriter(OutputOptions options);
+    void write(FrameResult const& result);
+private:
+    OutputOptions options_;
+    std::string runId_;
+};
+}