NEON-29: Freeze horizontal velocity on column tread wobble band.

When vlat&&ncol, XZ within ~0.92*ARRIVE_EPS, and vert_sep in a narrow band
above vertical-arrival noise, zero XZ velocity so nav slide cannot drive ~6 cm
Y oscillation on violet stairs. Descending fallback when column latch is off;
skip when goal is above feet (climb still needs XZ).

client/scripts/player.gd

@@ -38,6 +38,13 @@ const WALK_PEEL_SUSPEND_VERT_SEP: float = 0.48
 ## so shallow lips (~0.48 m) still peel; widened from 0.34 to cover ~0.35–0.47 m stair/goal gaps.
 const WALK_PEEL_SUSPEND_HORIZ_VERT_SEP: float = 0.46
 const WALK_PEEL_SUSPEND_HORIZ_DIST: float = 5.0
+## In [code]vlat && ncol[/code], when XZ is almost at arrival but [code]vert_sep[/code] sits in a tread
+## wobble band (~4.5–13 cm), full [member MOVE_SPEED] slide keeps pumping Y (NEON-16 ~0.89–0.95). Zero
+## horizontal [member velocity] for that tick so only floor snap settles height — narrow gates avoid
+## freezing open-floor approaches or long vertical offsets.
+const WALK_TREAD_FREEZE_HORIZ_FRAC: float = 0.92
+const WALK_TREAD_FREEZE_VERT_SEP_MIN: float = 0.045
+const WALK_TREAD_FREEZE_VERT_SEP_MAX: float = 0.13
 ## [method _walk_has_close_floor_probe_below] often flips on stairs: next tread is ~0.104 m down but
 ## [member WALK_CONTINUATION_MAX_BELOW_FEET] is 0.078 m, so rays reject the hit → peel + zero snap
 ## alternate with full snap each tick (~y≈1.0 jitter). Require this many consecutive probe-fail frames
@@ -495,6 +502,23 @@ func _walk_peel_suspend_near_goal(feet_y: float, horiz_dist: float) -> bool:
 	return vsep <= WALK_PEEL_SUSPEND_HORIZ_VERT_SEP and horiz_dist <= WALK_PEEL_SUSPEND_HORIZ_DIST
 
 
+func _walk_tread_freeze_horizontal_active(feet_y: float, horiz_dist: float) -> bool:
+	if not is_on_floor() or not _has_walk_goal:
+		return false
+	# Step-up / climb still needs XZ motion along the face.
+	if _auth_walk_goal.y > feet_y + 0.04:
+		return false
+	if horiz_dist > ARRIVE_EPS * WALK_TREAD_FREEZE_HORIZ_FRAC:
+		return false
+	var vsep: float = absf(_auth_walk_goal.y - feet_y)
+	if vsep <= WALK_TREAD_FREEZE_VERT_SEP_MIN or vsep > WALK_TREAD_FREEZE_VERT_SEP_MAX:
+		return false
+	if _walk_vert_route_latched and _walk_nav_column_steering:
+		return true
+	# [code]vlat[/code] can unlatch on long descents; keep freeze only when clearly dropping.
+	return _auth_walk_goal.y < feet_y - DESCEND_GOAL_Y_MARGIN
+
+
 func _walk_refresh_ledge_peel_debounce(feet_y: float, move_dir_xz: Vector2) -> void:
 	var probe_ok: bool = _walk_has_close_floor_probe_below(move_dir_xz)
 	var deep: bool = feet_y > _auth_walk_goal.y + WALK_DEEP_DESCENT_FEET_ABOVE_GOAL
@@ -1098,6 +1122,10 @@ func _physics_process(delta: float) -> void:
 	else:
 		_set_horizontal_velocity_toward(_auth_walk_goal, want_goal_h)
 
+	if _walk_tread_freeze_horizontal_active(feet_y, horiz_dist):
+		velocity.x = 0.0
+		velocity.z = 0.0
+
 	var walk_move_dir_xz: Vector2 = _resolve_walk_probe_dir_xz(feet_y, want_goal_h)
 	_walk_refresh_ledge_peel_debounce(feet_y, walk_move_dir_xz)