Reviewing the previous fix, which was itself unreviewed. `update` gave
each list the bind group layout of the pipeline that draws it by zipping
the layer's lists against `self.primitives`, but built those pipelines
afterwards -- so on any pass where one did not exist yet the zip yielded
nothing, and those lists kept no bind group and drew nothing. Measured
on startup: four layers had content while `self.primitives` was still
empty. It only looked right because those layers were marked dirty again
on a later frame and rebuilt then.
`build_pipelines` now runs before the layers, and the pairing is indexed
rather than zipped, so a primitive drawn before it was registered panics
instead of silently leaving its list unbuilt.
iris
89491a5949