feat(thermal): publish fully validated HDF5 histories atomically

include/fesa/results/thermal_results_writer.h

@@ -0,0 +1,26 @@
+#ifndef FESA_RESULTS_THERMAL_RESULTS_WRITER_H_
+#define FESA_RESULTS_THERMAL_RESULTS_WRITER_H_
+
+#include <filesystem>
+#include <vector>
+
+#include "fesa/analysis/thermal_analysis_state.h"
+#include "fesa/core/diagnostic.h"
+#include "fesa/core/status.h"
+
+namespace fesa {
+class Domain;
+
+/// @brief Persists a complete accepted thermal history atomically.
+class ThermalResultsWriter {
+ public:
+  virtual ~ThermalResultsWriter() = default;
+  /// @brief Writes every accepted thermal frame and diagnostics atomically.
+  /// @note The Domain and immutable state must outlive this call.
+  virtual Status Write(const std::filesystem::path& output_path,
+                       const Domain& domain, const ThermalAnalysisState& state,
+                       const std::vector<Diagnostic>& diagnostics) = 0;
+};
+}  // namespace fesa
+
+#endif  // FESA_RESULTS_THERMAL_RESULTS_WRITER_H_