Closes #14

core/dbc_decode_builder.h

@@ -23,7 +23,8 @@ public:
     /**
      * @brief Build runtime decode database.
      * @param source Parsed DBC database.
-     * @return Runtime-ready decode database.
+     * @return Immutable runtime snapshot independent of source lifetime.
+     * @throws std::invalid_argument for duplicate frame keys or signal names.
      */
     DecodeDatabase Build(const DbcDatabase &source) const;
 };