Land SYSTEM4-rooted Godot boot

engine/Age.Engine/Model/BlendKind.cs

@@ -1,6 +1,5 @@
 namespace Age.Engine.Model;
 
 /// <summary>How an object's surface composites onto the canvas. Opaque = straight copy; Alpha = source-alpha
-/// blend (fades). Additive (glow/flash, native blit mode 2/3) is a documented seam — NOT implemented in the
-/// blend/transparency slice; see docs/superpowers/specs/2026-07-08-blend-transparency-design.md.</summary>
+/// blend (fades); Additive = native SRCALPHA/ONE glow composition.</summary>
 public enum BlendKind { Opaque, Alpha, Additive }