World Partition - HLOD: baked HLOD textures contain unresolved runtime virtual texture content

Baking HLODs for actors that sample Runtime Virtual Textures produces incorrect baked textures: blurry or unresolved RVT tiles, fully black tiles on the first bake of an editor session, and washed-out/overexposed tiles in the Normal/Metallic/Roughness/Specular channels. Rebuilding sometimes hides the problem; commandlet builds are more reliable than editor builds, which makes this intermittent and easy to ship unnoticed.

1. Fresh editor session, World Partition map with a landscape (or meshes) sampling an RVT, landscape never loaded.
2. Build HLODs for a region containing the RVT writers.
3. Inspect the generated HLOD textures: first-build tiles are black/washed out; tiles are blurry where the adaptive RVT never converged.