Both tests composed only the fused half and rendered it through the plain
path. That was correct while every operation was a point operation; with a
kernel in the chain the fused pass stops short of the output transform, so
the render was rejected and the operation-block count was one too high.
Compose both halves and dispatch them together, and assert that each
operation reaches exactly one of the two stages rather than counting blocks
- so the next kernel added extends the coverage instead of breaking it.
dtourolle
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