denoise_temporal_rgba16f

One temporal accumulation pass: reprojects the previous frame's estimate onto this frame through @scene.motion, admits it where the guide says it belongs to the same surface, and mixes this frame's sample in.

The pass itself is @builtin::systems.denoising.dn_temporal, which both format variants include — see that module for what the bindings mean and how a reprojected tap is admitted.

Writes rgba16f; the pair of these covers the formats a filter is built for.