feat(util): add RgbaToVector4 and Vector4ToRgba helpers for color picker

HellionChat/Util/ColourUtil.cs

@@ -30,6 +30,30 @@ internal static class ColourUtil
         );
     }
 
+    internal static Vector4 RgbaToVector4(uint rgba)
+    {
+        var (r, g, b) = RgbaToRgbComponents(rgba);
+        var a = (byte)(rgba & 0xFFu);
+        return new Vector4(r / 255f, g / 255f, b / 255f, a / 255f);
+    }
+
+    internal static uint Vector4ToRgba(Vector4 col)
+    {
+        // Clamp guards against future ImGuiColorEditFlags.HDR feeding out-of-range
+        // components: a raw byte-cast would wrap (e.g. (byte)Math.Round(2.0f*255)=254).
+        // Mirrors the ApplyAlpha clamping pattern in this file.
+        var r = Math.Clamp(col.X, 0f, 1f);
+        var g = Math.Clamp(col.Y, 0f, 1f);
+        var b = Math.Clamp(col.Z, 0f, 1f);
+        var a = Math.Clamp(col.W, 0f, 1f);
+        return ComponentsToRgba(
+            (byte)Math.Round(r * 255),
+            (byte)Math.Round(g * 255),
+            (byte)Math.Round(b * 255),
+            (byte)Math.Round(a * 255)
+        );
+    }
+
     internal static uint Vector4ToAbgr(Vector4 col)
     {
         return RgbaToAbgr(