Support for Debug Codes - Dnnn (#19225)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/gcode/control/T.cpp

@@ -46,7 +46,7 @@
  *   Tx   Same as T?, but nozzle doesn't have to be preheated. Tc requires a preheated nozzle to finish filament load.
  *   Tc   Load to nozzle after filament was prepared by Tc and nozzle is already heated.
  */
-void GcodeSuite::T(const uint8_t tool_index) {
+void GcodeSuite::T(const int8_t tool_index) {
 
   DEBUG_SECTION(log_T, "T", DEBUGGING(LEVELING));
   if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("...(", tool_index, ")");