NEON-29: Hold-threshold stable idle + physics HUD coords

While _idle_stable_latched, use STABLE_IDLE_FLOOR_HOLD_MIN_UP_DOT (0.992) for
idle_support floor flatness so tread-edge normal flicker does not unlatch as
often. idle_support_is_stable gains optional min_flat_up_dot; unlatch streak 8.
Prototype position label updates in main _physics_process. Add GdUnit for param.

client/scripts/main.gd

@@ -7,7 +7,8 @@ extends Node3D
 ## (see `isometric_follow_camera.gd`).
 ## Prototype: two random short bumps (sibling StaticBody3D under NavigationRegion3D; see
 ## `random_floor_bumps.gd`) before nav bake.
-## Prototype HUD: world `CharacterBody3D` position in `UICanvas/PlayerPositionLabel`.
+## Prototype HUD: world `CharacterBody3D` position in `UICanvas/PlayerPositionLabel`
+## (updated in `_physics_process` so it matches physics ticks).
 
 const MOVE_REJECT_MSG_SECONDS: float = 4.0
 
@@ -35,7 +36,7 @@ var _dev_obstacle_smoke: Node3D
 
 
 func _ready() -> void:
-	set_process(true)
+	set_physics_process(true)
 	set_process_unhandled_key_input(true)
 	await get_tree().process_frame
 	_dev_obstacle_smoke = get_node_or_null("World/NavigationRegion3D/Obstacle") as Node3D
@@ -57,7 +58,7 @@ func _ready() -> void:
 		_radius_preview.call("setup_player", _player)
 
 
-func _process(_delta: float) -> void:
+func _physics_process(_delta: float) -> void:
 	if not is_instance_valid(_player) or not is_instance_valid(_player_pos_label):
 		return
 	var p: Vector3 = _player.global_position

client/scripts/player.gd

@@ -30,10 +30,12 @@ const IDLE_RIM_MIN_FLOOR_UP_DOT: float = 0.968
 ## Stable flat idle support: skip corrective idle motion when support is effectively level.
 ## Below 1.0 so Jolt seam normals do not flicker across the threshold (idle XZ noise).
 const STABLE_IDLE_FLOOR_MIN_UP_DOT: float = 0.999
+## While [member _idle_stable_latched], allow slightly tilted reported normals (tread/riser edge).
+const STABLE_IDLE_FLOOR_HOLD_MIN_UP_DOT: float = 0.992
 ## Rare edge contacts can keep corrective nudges alive forever; budget them, then hold x/z.
 const IDLE_MANUAL_CORRECTION_MAX_TICKS: int = 8
 ## Consecutive unstable-idle physics ticks before leaving latched stable idle (thin tread lip).
-const STABLE_IDLE_UNLATCH_TICKS: int = 5
+const STABLE_IDLE_UNLATCH_TICKS: int = 8
 ## Horizontal nudge per tick for rim / straddle settle (**`_maybe_idle_rim_settle_nudge`**).
 const IDLE_RIM_SETTLE_STEP: float = 0.004
 ## Used by tests and vertical routing checks (feet vs goal surface).
@@ -397,11 +399,15 @@ static func idle_slide_contacts_are_ridged(slide_normals: Array[Vector3]) -> boo
 
 
 static func idle_support_is_stable(
-	on_floor: bool, floor_normal: Vector3, slide_normals: Array[Vector3], loose_ticks: int
+	on_floor: bool,
+	floor_normal: Vector3,
+	slide_normals: Array[Vector3],
+	loose_ticks: int,
+	min_flat_up_dot: float = STABLE_IDLE_FLOOR_MIN_UP_DOT,
 ) -> bool:
 	if not on_floor:
 		return false
-	if floor_normal.dot(Vector3.UP) < STABLE_IDLE_FLOOR_MIN_UP_DOT:
+	if floor_normal.dot(Vector3.UP) < min_flat_up_dot:
 		return false
 	# Post-stop **ridged** slides (tread + riser) used to force unstable idle for the entire
 	# `loose_ticks` window even when the **floor** is level — e.g. idle on a flat approach tread
@@ -425,8 +431,13 @@ func _current_slide_normals() -> Array[Vector3]:
 
 
 func _stable_idle_support() -> bool:
+	var min_dot: float = (
+		STABLE_IDLE_FLOOR_HOLD_MIN_UP_DOT
+		if _idle_stable_latched
+		else STABLE_IDLE_FLOOR_MIN_UP_DOT
+	)
 	return idle_support_is_stable(
-		is_on_floor(), get_floor_normal(), _current_slide_normals(), _floor_angle_loose_ticks
+		is_on_floor(), get_floor_normal(), _current_slide_normals(), _floor_angle_loose_ticks, min_dot
 	)
 
 

client/test/player_test.gd

@@ -62,6 +62,15 @@ func test_idle_support_is_stable_false_when_floor_is_not_flat_enough() -> void:
 	assert_that(stable).is_false()
 
 
+func test_idle_support_is_stable_min_flat_up_dot_parameter() -> void:
+	var slide_normals: Array[Vector3] = [Vector3.UP]
+	var floor_n: Vector3 = Vector3(0.05, 0.99875, 0.0).normalized()
+	var strict: bool = PLAYER_SCRIPT.idle_support_is_stable(true, floor_n, slide_normals, 0, 0.999)
+	var holdish: bool = PLAYER_SCRIPT.idle_support_is_stable(true, floor_n, slide_normals, 0, 0.992)
+	assert_that(strict).is_false()
+	assert_that(holdish).is_true()
+
+
 func test_idle_support_is_stable_true_when_flat_floor_has_extra_contacts() -> void:
 	var slide_normals: Array[Vector3] = [Vector3.UP, Vector3(0.0, 0.6, 0.8).normalized()]
 	var stable: bool = PLAYER_SCRIPT.idle_support_is_stable(true, Vector3.UP, slide_normals, 0)