Save the bufw for textures as well, to match fbs.
Check the entire FB range for textures.

Using lower_bound/upper_bound should not be very slow.
Log when render to texture formats differ.
Detect tex subarea renders and palette renders.

But right now, just drawing the original, which isn't really correct.
Cut down the scan range to avoid perf hit.

Probably no perf hit anyway.  Should have the same functionality.
Don't bind odd render-to-texture when copying mem.