NS-23: fix false arrival when leaving bump tops

VERT_ARRIVE_EPS (0.16) was larger than the bump rise (~0.12–0.15), so a
floor click beside the plateau often satisfied arrival (horiz + vert) on
the first frame and cleared the walk goal before any motion.

Tighten vertical arrival to 0.055. Add a steer fallback when the target
shares xz but is lower (plateau vs floor underfoot) so we still pick a
horizontal escape toward the rim.

client/scripts/player.gd

@@ -5,7 +5,9 @@ extends CharacterBody3D
 
 const MOVE_SPEED: float = 5.0
 const ARRIVE_EPS: float = 0.35
-const VERT_ARRIVE_EPS: float = 0.16
+## Must be **below** NS-19 bump rise (~0.12–0.15) or we "arrive" while still on the plateau when the
+## goal is on the floor beside the bump (small horiz offset + ~0.15 m vertical).
+const VERT_ARRIVE_EPS: float = 0.055
 const MAX_CLIMB_SPEED: float = 2.6
 const MAX_DESCENT_SPEED: float = 2.2
 const DIRECT_APPROACH_RADIUS: float = 0.85
@@ -57,6 +59,12 @@ func _steer_toward_world_point(point: Vector3) -> void:
 		var desired: Vector3 = delta.normalized() * MOVE_SPEED
 		desired.y = clampf(desired.y, -MAX_DESCENT_SPEED, MAX_CLIMB_SPEED)
 		velocity = desired
+	elif dy < -0.04:
+		# Goal is lower and almost same xz (e.g. floor under the plateau): still need rim escape.
+		var escape_h := Vector3(-global_transform.basis.z.x, 0.0, -global_transform.basis.z.z)
+		if escape_h.length_squared() < 1e-8:
+			escape_h = Vector3(1.0, 0.0, 0.0)
+		velocity = escape_h.normalized() * MOVE_SPEED
 	else:
 		velocity = Vector3.ZERO