Fix flashlight dim being applied before slider start time

Closes ppy#26515.

Compare ppy#26053.

osu.Game.Rulesets.Osu/Mods/OsuModFlashlight.cs

@@ -50,7 +50,7 @@ public partial class OsuModFlashlight : ModFlashlight<OsuHitObject>, IApplicable
         public void ApplyToDrawableHitObject(DrawableHitObject drawable)
         {
             if (drawable is DrawableSlider s)
-                s.Tracking.ValueChanged += flashlight.OnSliderTrackingChange;
+                s.Tracking.ValueChanged += _ => flashlight.OnSliderTrackingChange(s);
         }
 
         private partial class OsuFlashlight : Flashlight, IRequireHighFrequencyMousePosition
@@ -66,10 +66,10 @@ public OsuFlashlight(OsuModFlashlight modFlashlight)
                 FlashlightSmoothness = 1.4f;
             }
 
-            public void OnSliderTrackingChange(ValueChangedEvent<bool> e)
+            public void OnSliderTrackingChange(DrawableSlider e)
             {
                 // If a slider is in a tracking state, a further dim should be applied to the (remaining) visible portion of the playfield.
-                FlashlightDim = e.NewValue ? 0.8f : 0.0f;
+                FlashlightDim = Time.Current >= e.HitObject.StartTime && e.Tracking.Value ? 0.8f : 0.0f;
             }
 
             protected override bool OnMouseMove(MouseMoveEvent e)