feat(cpp-object-oriented-modular-refactoring): step 12 - material-property-hierarchy

include/fesa/core/source_identity.h

@@ -8,6 +8,9 @@
 
 namespace fesa {
 
+/// @brief Identifies a semantic entity by its stable collection position.
+using EntityIndex = std::uint32_t;
+
 /// @brief Identifies the input location that produced an item or diagnostic.
 struct SourceLocation {
   std::filesystem::path file;