test: close render object id coverage gaps

engine/assets/builtin/shaders/object-id-outline.shader

@@ -46,9 +46,9 @@ Shader "Builtin Object Id Outline"
 
     bool IsSelectedObject(float4 objectIdColor)
     {
-        // Object-id surfaces encode the low 32 bits across RGBA, so low-valued
-        // runtime ids legitimately have zero alpha. Only the all-zero clear
-        // color should be treated as "no object".
+        // Object-id surfaces encode the formal 32-bit render object id across
+        // RGBA. Low-valued ids legitimately have zero alpha, so only the
+        // all-zero clear color should be treated as "no object".
         if (all(abs(objectIdColor) <= float4(
                 0.0025,
                 0.0025,