Draw Navara world meshes in the overlay pass after tone mapping

Meshes now go through the same overlay as sprites and lines, so their
colours are the ones asked for without undoing the view's exposure. The
contract suite no longer carries the mesh colour check as a known
failure on Navara.

docs/GLOBE-PRIMITIVES.md

@@ -538,9 +538,10 @@ Cesium draws a synchronous Primitive with a flat material, no back-face
 culling and no depth writes. Colour, image and visibility changes retain the
 primitive; geometry, pick-id and depth-test changes replace it. The engine
 requests frames while the primitive or its image is preparing. Navara draws
-local coordinates relative to a double-precision world origin in its
-transparent scene pass after tone mapping, with scene depth and triangle
-picking. Their authored colours are blended in display space.
+local coordinates relative to a double-precision world origin in the shared
+overlay pass after tone mapping and anti-aliasing, the pass that draws sprites
+and lines, with scene depth and triangle picking. Their authored colours are
+blended in display space.
 Both engines own geometry, material and texture disposal. The fake engine
 keeps the same state and tests triangle intersections for picks.