NEON-29: Cap walk speed on tread stability band for stair jitter.

Steering reverse clamp was reverted (blocked arrival). Instead, when on floor
and (vlat && ncol && vert_sep band) or tight XZ + small vert_sep, clamp
horizontal speed to 1.35 m/s so move_and_slide does not drive riser ping-pong
at full MOVE_SPEED. Bump path steer min lookahead 0.22→0.28 m.

client/scripts/player.gd

@@ -24,8 +24,8 @@ const NAV_COLUMN_STEER_ENTER_DIST: float = 0.74
 const NAV_COLUMN_STEER_EXIT_DIST: float = 0.97
 ## First path waypoint used for column steer must be at least this far in XZ. [method NavigationAgent3D.get_next_path_position]
 ## can sit ~4 cm from the capsule; Jolt slides ~4 cm/tick → the “toward next” vector flips 180° every frame
-## (`vlat && ncol` NEON-16 traces). A 22 cm gate matches foot-scale probes and stays stable on treads.
-const NAV_PATH_STEER_MIN_LOOKAHEAD: float = 0.22
+## (`vlat && ncol` NEON-16 traces). ~28 cm reduces waypoint flip on treads without starving short segments.
+const NAV_PATH_STEER_MIN_LOOKAHEAD: float = 0.28
 ## If lookahead steering points more than ~105° from the click direction (XZ), use direct goal steer instead.
 const NAV_PATH_STEER_MIN_GOAL_DOT: float = -0.25
 ## While [code]vlat && ncol[/code], ledge peel + zero floor snap fight [method move_and_slide] on approach treads
@@ -38,6 +38,11 @@ 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
+## On-floor only: cap horizontal speed in [method _walk_tread_jitter_damp_active] so full [member MOVE_SPEED]
+## does not hammer stair risers after peel/snap debounce (still ~mm–cm Y noise at y≈1.09).
+const WALK_TREAD_STABILITY_MAX_HORIZ_SPEED: float = 1.35
+## With [code]vlat[/code] false, only damp when this close in XZ — avoids slowing long same-level approaches.
+const WALK_TREAD_STABILITY_DAMP_HORIZ_DIST: float = 1.05
 ## [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
@@ -496,6 +501,25 @@ 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_jitter_damp_active(feet_y: float, horiz_dist: float) -> bool:
+	if not _has_walk_goal or not is_on_floor():
+		return false
+	var vsep: float = absf(_auth_walk_goal.y - feet_y)
+	if _walk_vert_route_latched and _walk_nav_column_steering and vsep < WALK_PEEL_SUSPEND_VERT_SEP:
+		return true
+	return vsep <= WALK_PEEL_SUSPEND_HORIZ_VERT_SEP and horiz_dist <= WALK_TREAD_STABILITY_DAMP_HORIZ_DIST
+
+
+func _walk_apply_tread_horizontal_speed_cap() -> void:
+	var vxz := Vector2(velocity.x, velocity.z)
+	var sp: float = vxz.length()
+	if sp <= WALK_TREAD_STABILITY_MAX_HORIZ_SPEED + 1e-6:
+		return
+	var scale: float = WALK_TREAD_STABILITY_MAX_HORIZ_SPEED / sp
+	velocity.x = vxz.x * scale
+	velocity.z = vxz.y * scale
+
+
 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
@@ -1099,6 +1123,9 @@ func _physics_process(delta: float) -> void:
 	else:
 		_set_horizontal_velocity_toward(_auth_walk_goal, want_goal_h)
 
+	if _walk_tread_jitter_damp_active(feet_y, horiz_dist):
+		_walk_apply_tread_horizontal_speed_cap()
+
 	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)