cutting plywood is a major challenge for shops that want to use as few power tools as possible

The answers in this StackExchange post are useful and illuminating. Their main conclusion is "plywood is a modern material that requires modern tools to cut it cleanly". However, there are some good detailed tips there for making it work with hand tools.

a circular saw

The option that would make these cuts easiest would be to buy this DeWalt circular saw, and a carbide-tipped blade. But that is one extra power tool that I don't necessarily have the space for.

jigsaw

There are various bits of advice here and here on which blades and techniques to use. The second link suggests the Diablo Bi-Metal Jig Saw Blade for Wood (that has bi-directional cutting).

Other blade recommendations: [1] [2]

a rough cut, followed by a trim router to finish to the line

As suggested here.

Although this would also require purchase of a new electric tool, I think I already need to buy that for a separate task — cutting T-slots in wood.