feat: add double-barrel shotgun weapon, player movement state machine, and procedural sound assets

movement/states/state_air.gd

@@ -81,6 +81,8 @@ func update(delta: float) -> void:
 			machine.on_ground = false
 			machine.jump_buffer_time = 0.0
 			machine.register_chain_mechanic("bunny_hop")
+			if player.jump_player:
+				player.jump_player.play()
 			# Stay in air state
 			return
 
@@ -92,6 +94,8 @@ func update(delta: float) -> void:
 		player.velocity.y = params.double_jump_velocity
 		machine.current_jump_count += 1
 		machine.register_chain_mechanic("double_jump")
+		if player.double_jump_player:
+			player.double_jump_player.play()
 		return
 
 	# ── Wall run transition ───────────────────────────────────────────────