docs(render): Phase A8.F — note why MarkAndPunchNdc omits DepthClamp (NDC z=0)

src/AcDream.App/Rendering/IndoorCellStencilPipeline.cs

@@ -308,6 +308,9 @@ public sealed unsafe class IndoorCellStencilPipeline : IDisposable
         _gl.Clear(ClearBufferMask.StencilBufferBit);
 
         // Step 1: mark bit 1.
+        // No DepthClamp here (unlike MarkAndPunch): MarkAndPunch draws world-space portal
+        // polygons that can fall outside [near,far]; these verts are already NDC with z=0,
+        // always within the depth range, so there is nothing to clamp.
         _gl.ColorMask(false, false, false, false);
         _gl.DepthMask(false);
         _gl.DepthFunc(DepthFunction.Always);