You could consider two coops: a summer one (hoop coop or similar) by the garden, and a more weather-proof winter coop. Two coops also means you can raise chicks in one while the adult chickens are in the other one, which might be useful in the future.I think what I’m really looking for is a coop that isn’t a tractor but isn’t a big shed- something in between, where moving it is a possibility with just two people, no machines needed. I’ll keep researching, thank you!!!
For semi-portable and semi-predator-resistant, you might look into something like a chain link dog kennel. I had one that was a set of panels 6 feet high and 10 feet long/wide. I could take off the corner connectors (a few minutes' work with a wrench) and drag the panels one-by-one to a new location, then put them back together. I even assembled it around a big tree trunk a few times, when I wanted the chickens to destroy the weeds at the base of the tree. Moving it probably took less than an hour when I was working alone (slightly faster with an adult to help, much slower with a small child to "help".)
Of course chain link is not perfect: weasels can go through it, raccoons can reach through it or climb over it, chickens can fly over unless it is covered, and animals could dig underneath. But it will keep the chickens from walking into the garden to scratch, and it will keep any stray dogs from just grabbing a chicken when they come by. If you add a top, and cover the sides with hardware cloth (1/2" mesh) it's a lot more secure, but also more bother to move around. I read of someone else who attached plywood to parts of two sides, making a solid corner that raccoons could not reach into (the chickens would run there to try to hide from the raccoons.)
There are other styles of dog kennel panels that have roofs as well (some are just a tarp, some have actual metal mesh panels.) All of them tend to be expensive unless you get them second hand, but all of them can be put together/taken apart for moving. Unfortunately, all of them also have large mesh on the sides. But large mesh may be enough for daytime use, if the chickens have a more secure place for the night.
Dog kennels can range from great to useless, depending on a bunch of different factors about both the kennel and your conditions. I have found them useful, with modifications or special consideration for certain details.