Automated review on the lighter paths

The other half of #698. If presentation paths are to move faster on lighter review, that
lighter review has to be real, otherwise the boundary just means less review.

An automated pass on those paths should be required before merge, so the lighter route is a
different kind of scrutiny rather than an absence of it.

Depends on: #698, which decides which paths these are.

Steps

• Automated review pass runs on the lighter paths
• Required before merge on those paths
• Its findings appear in the pull request summary

Done when

Every path has either engineer review or an enforced automated pass, and none has neither.