chore(multiplayer): Phase 0 refactors + graphics/perf settings groundwork

Lands the non-networked Phase 0 tasks from multiplayer-todo.md (ship/camera/
arena refactors, sim constants, background FPS handling) plus a first pass
at exposing graphics/performance settings (presets, resolution scaling,
vsync, FPS cap, perf overlay) and a GPU profiling harness for the
real-hardware follow-up in task 0.15b.

Game/scripts/hud_instrument.gd

@@ -7,6 +7,13 @@ extends Control
 # _process (smoothing 1-2 distinct fields) and _draw (entirely bespoke).
 
 const SMOOTHING := 12.0
+# _draw does real work (text shaping, building point arrays); nobody can
+# perceive an instrument repainting faster than this, so redraws are paced
+# to it independently of the render frame rate — value smoothing itself
+# still runs every _process call, only the (expensive) repaint is throttled.
+const REDRAW_INTERVAL := 1.0 / 60.0
+
+var _time_since_redraw := 0.0
 
 
 static func lerp_angle_deg(from: float, to: float, weight: float) -> float:
@@ -23,3 +30,12 @@ static func angle_delta_deg(from: float, to: float) -> float:
 
 func _smoothing_weight(delta: float) -> float:
 	return 1.0 - exp(-SMOOTHING * delta)  # frame-rate independent
+
+
+# Call instead of queue_redraw() directly once a subclass's _process has
+# decided the smoothed value moved enough to warrant a repaint.
+func _throttled_redraw(delta: float) -> void:
+	_time_since_redraw += delta
+	if _time_since_redraw >= REDRAW_INTERVAL:
+		_time_since_redraw = 0.0
+		queue_redraw()