Add H.264 inference session recording and replay

include/inference_session.hpp

@@ -0,0 +1,38 @@
+#pragma once
+#include "camera.hpp"
+#include "frame_result.hpp"
+#include <nlohmann/json.hpp>
+#include <filesystem>
+#include <fstream>
+#include <opencv2/videoio.hpp>
+
+namespace cms {
+struct PipelineConfig;
+// H.264/MP4 plus a matching frame index and per-frame inference records.
+// finish() flushes the encoder and marks the session replayable.
+class SessionWriter {
+public:
+    explicit SessionWriter(PipelineConfig const& config);
+    void write(FrameResult const& result, nlohmann::json const& stages,
+               nlohmann::json const* source = nullptr);
+    void finish();
+private:
+    std::filesystem::path directory_;
+    std::ofstream index_;
+    cv::VideoWriter video_;
+    int width_{},height_{};
+    std::uint64_t count_{};
+    bool finished_{};
+};
+class SessionReader {
+public:
+    explicit SessionReader(PipelineConfig& config);
+    std::optional<CapturedFrame> read();
+private:
+    std::filesystem::path directory_;
+    std::ifstream index_;
+    cv::VideoCapture video_;
+    int width_{},height_{};
+    std::uint64_t count_{},lastFrame_{},expectedCount_{};
+};
+}