feat(linear-static-3d-euler-beam): step 8 - core-diagnostics

include/fesa/core/source_identity.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <filesystem>
+#include <string>
+
+namespace fesa {
+
+// Identifies the physical input location that produced a model item or diagnostic.
+struct SourceLocation {
+    std::filesystem::path file;
+    std::size_t line;
+};
+
+// Preserves both semantic and raw-text forms of an input entity identity.
+struct SourceEntityId {
+    std::string instanceName;
+    std::int64_t sourceLabel;
+    std::string sourceLabelText;
+};
+
+} // namespace fesa