refactor: escape newlines in prompt logs and clarify source separators (#2106)

src/core/util.h

@@ -29,6 +29,7 @@ bool contains(const std::string& str, const std::string& substr);
 std::string sd_format(const char* fmt, ...);
 
 void replace_all_chars(std::string& str, char target, char replacement);
+std::string escape_newlines(const std::string& text);
 
 int round_up_to(int value, int base);