perf(hud): stop flight instruments redrawing when values have settled

hud_gauge, hud_attitude_indicator, and hud_heading_tape now skip
queue_redraw() when the newly-lerped value hasn't moved past a small
epsilon, instead of redrawing every frame forever. Angle-wrapping
values (heading, attitude roll) use a new shared angle_delta_deg
helper on HudInstrument so the wrap boundary doesn't read as a false
jump.

HUD.tscn's Instruments node now sets process_mode = 1 (PAUSABLE),
overriding the inherited ALWAYS mode from the HUD root so instruments
stop processing during the post-match pause freeze, while sibling
ResultOverlay keeps running its win-screen tween.

Game/scripts/hud_gauge.gd

@@ -26,8 +26,14 @@ func set_value(value: float) -> void:
 
 func _process(delta: float) -> void:
 	var t := _smoothing_weight(delta)
-	_value = lerpf(_value, _target, t)
-	queue_redraw()
+	var new_value := lerpf(_value, _target, t)
+	# Redraw threshold scales with the gauge's own range so it stays
+	# imperceptible whether this is a 0-12 altitude gauge or a 0-100 thrust
+	# bar, while skipping the redraw once the lerp has visually settled.
+	var changed := absf(new_value - _value) > max_value * 0.001
+	_value = new_value
+	if changed:
+		queue_redraw()
 
 
 func _draw() -> void: