NS-23: Apply gravity when airborne so bump ledges are not sticky

Horizontal seek only sets vx/vz; zero vy only on floor. Use project default
gravity vector when not on floor (with and without walk goal) so stepping
off NS-19 bumps can fall to the lower surface instead of hanging with vy=0.

client/scripts/player.gd

@@ -2,9 +2,9 @@ extends CharacterBody3D
 
 ## NS-23: Follow server move target on walkable geometry.
 ##
-## Horizontal velocity toward nav waypoint or goal only; `velocity.y` stays 0. Height along ramps
+## Horizontal seek sets `velocity.x`/`z` only. On floor `velocity.y` is cleared; in air project
-## and steps comes from `move_and_slide` + floor_* on CharacterBody3D. Move **legality** (step,
+## gravity applies so walking off bumps/steps can descend (vy was never forced to 0 while airborne).
-## distance, bounds) is server MoveCommand only — not reimplemented here.
+## Move **legality** is server MoveCommand only — not reimplemented here.
 ##
 ## Nav for detours; short local step-down (feet vs goal Y, not body origin) may bypass waypoints.
 
@@ -106,13 +106,33 @@ func _set_horizontal_velocity_toward(point: Vector3) -> void:
 	var dh: Vector3 = Vector3(point.x - pos.x, 0.0, point.z - pos.z)
 	if dh.length_squared() < 1e-10:
 		dh = Vector3(1.0, 0.0, 0.0)
-	velocity = dh.normalized() * MOVE_SPEED
+	var h: Vector3 = dh.normalized() * MOVE_SPEED
-	velocity.y = 0.0
+	velocity.x = h.x
+	velocity.z = h.z
 
 
-func _physics_process(_delta: float) -> void:
+func _apply_vertical_velocity_for_floor_or_gravity(delta: float) -> void:
+	if is_on_floor():
+		velocity.y = 0.0
+		return
+	var gmag: float = float(ProjectSettings.get_setting("physics/3d/default_gravity", 9.8))
+	var gvec: Variant = ProjectSettings.get_setting(
+		"physics/3d/default_gravity_vector", Vector3(0.0, -1.0, 0.0)
+	)
+	if gvec is Vector3:
+		velocity += (gvec as Vector3) * gmag * delta
+	else:
+		velocity.y -= gmag * delta
+
+
+func _physics_process(delta: float) -> void:
 	if not _has_walk_goal:
-		velocity = Vector3.ZERO
+		if is_on_floor():
+			velocity = Vector3.ZERO
+		else:
+			velocity.x = 0.0
+			velocity.z = 0.0
+			_apply_vertical_velocity_for_floor_or_gravity(delta)
 		move_and_slide()
 		return
 
@@ -132,11 +152,13 @@ func _physics_process(_delta: float) -> void:
 	var nav_map: RID = _nav_agent.get_navigation_map()
 	if NavigationServer3D.map_get_iteration_id(nav_map) == 0:
 		_set_horizontal_velocity_toward(_auth_walk_goal)
+		_apply_vertical_velocity_for_floor_or_gravity(delta)
 		move_and_slide()
 		return
 
 	if _nav_short_step_down_use_goal_direct():
 		_set_horizontal_velocity_toward(_auth_walk_goal)
+		_apply_vertical_velocity_for_floor_or_gravity(delta)
 		move_and_slide()
 		return
 
@@ -152,4 +174,5 @@ func _physics_process(_delta: float) -> void:
 		else:
 			_set_horizontal_velocity_toward(_auth_walk_goal)
 
+	_apply_vertical_velocity_for_floor_or_gravity(delta)
 	move_and_slide()