Enabling FXAA with the water continuation split active renders the scene
into a corner of the frame. The two interact somewhere I have not found:
FXAA sets its own viewport and scissor before its quad, its targets are
created at the swapchain extent, and the layouts the split leaves behind
are the ones its transition expects — so the fault is not visible in the
code I have read.
Hold the split off on that path for now. Water goes back into the scene
pass there, which means FXAA users get the end-of-frame refraction copy
again and the ghosting that comes with it, but a correct picture. This is
a mitigation, not a diagnosis, and should be removed once the actual
interaction is found.
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