Add MVP footstep audio placeholders

Docs/TechnicalDesignDocument.md

@@ -316,6 +316,13 @@ because the controller is silent until loops are assigned; placeholder or final
 audio can be added by setting the exposed sound properties on the placed
 controller or a Blueprint child.
 
+Player movement audio starts with native footstep placeholders on
+`AAgrarianGameCharacter`. The character owns a spatialized
+`FootstepAudioComponent` plus assignable walk, sprint, crouch, and prone sound
+slots. Cadence is state-aware and driven by horizontal movement, so the MVP can
+remain silent until placeholder or final surface-aware cues are assigned while
+still giving designers a real hook for step audio in packaged builds.
+
 Campfires expose native extinguish logic through `AAgrarianCampfire::Extinguish`.
 Extinguishing clears remaining fuel, turns off replicated lit state, and reuses
 the same visual update path as natural fuel depletion.