fix: resolve all CI errors - remove unused Color4Extensions usings, fix Colour4/Matrix3x2/Vector2/Key migration issues

Agent-Logs-Url: https://github.com/winnerspiros/osu/sessions/d5e0a29e-7e36-48de-ab95-334865fa54ac

Co-authored-by: winnerspiros <1675249+winnerspiros@users.noreply.github.com>

Author: Copilot

osu.Game/Graphics/Backgrounds/Triangles.cs

@@ -164,7 +164,7 @@ protected override void Update()
                     particle.Position.Y = newY;
                 }
 
-                particle.Colour.A = adjustedAlpha;
+                particle.Colour = new Colour4(particle.Colour.R, particle.Colour.G, particle.Colour.B, adjustedAlpha);
                 parts[i] = particle;
             }
 

osu.Game/Graphics/Containers/WaveContainer.cs

@@ -5,7 +5,6 @@
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Audio.Sample;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Effects;

osu.Game/Graphics/Cursor/OsuTooltipContainer.cs

@@ -2,7 +2,6 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using osu.Framework.Allocation;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Cursor;

osu.Game/Graphics/UserInterface/DialogButton.cs

@@ -3,7 +3,6 @@
 
 using System;
 using osu.Framework;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Colour;
 using osu.Framework.Graphics.Containers;

osu.Game/Graphics/UserInterface/LoadingSpinner.cs

@@ -2,7 +2,6 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Diagnostics;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Colour;
 using osu.Framework.Graphics.Containers;

osu.Game/Graphics/UserInterface/Nub.cs

@@ -4,7 +4,6 @@
 using System;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Effects;

osu.Game/Graphics/UserInterface/OsuAnimatedButton.cs

@@ -2,7 +2,6 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using osu.Framework.Allocation;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Effects;

osu.Game/Graphics/UserInterface/OsuButton.cs

@@ -2,7 +2,6 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using osu.Framework.Allocation;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;

osu.Game/Graphics/UserInterface/OsuContextMenu.cs

@@ -2,7 +2,6 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using osu.Framework.Allocation;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Effects;
 using osu.Framework.Graphics.UserInterface;

osu.Game/Graphics/UserInterface/OsuDropdown.cs

@@ -6,7 +6,6 @@
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Audio.Sample;
-using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Sprites;