Update input_status.md

Author: taohsu

components/control/quantity_input/dsm/guideline/input_status.md

@@ -1 +1,7 @@
-/
+### Input status
+
+**`Empty`** The Empty state indicates that the quantity input is blank with no content or placeholder, a neutral starting point.
+
+**`Empty (Placeholder)`** The Empty with Placeholder state provides a hint or guidance inside the field to suggest expected input.
+
+**`Filled`** The Filled state shows that the user has entered valid content into the field, replacing any placeholder.