fix: replace unsafe fixed-size buffers with dynamic formatting helpers; add util format helpers; centralize log_on_line cleanup

v0/util.h

@@ -0,0 +1,27 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+#include <stdarg.h>
+#include <stddef.h>
+
+/**
+ * Formats a string using printf-style formatting and returns a newly allocated string.
+ * The caller is responsible for freeing the returned string.
+ * 
+ * @param fmt The format string.
+ * @param ... The values to format.
+ * @return A newly allocated string containing the formatted output.
+ */
+char* format_string(const char* fmt, ...);
+
+/**
+ * Formats a string using printf-style formatting with a va_list and returns a newly allocated string.
+ * The caller is responsible for freeing the returned string.
+ * 
+ * @param fmt The format string.
+ * @param args The va_list of values to format.
+ * @return A newly allocated string containing the formatted output.
+ */
+char* format_string_va(const char* fmt, va_list args);
+
+#endif