refactor: extract character handling into separate method and add ANSI fallback support

Extract the inline character processing logic from the REPL's main loop into a dedicated `handleChar()` method that returns a boolean to indicate whether the loop should exit. Add `_allowAnsi` flag and corresponding getter/setters for cursor and line to support a simpler fallback REPL when ANSI escape sequences are unavailable.

src/optional/wren_opt_meta.c

@@ -46,7 +46,7 @@ void metaGetModuleVariables(WrenVM* vm) {
     return;
   }
     
-  ObjModule* module = AS_MODULE(moduleValue);  
+  ObjModule* module = AS_MODULE(moduleValue);
   ObjList* names = wrenNewList(vm, module->variableNames.count);
   vm->apiStack[0] = OBJ_VAL(names);