Wanted to update everyone who was helping me brainstorm this: I finally laid eyes on the culprit this morning. A very chubby little rat! She scurried off as soon as I came out (making great use of the
fence boards as a little mini-highway) and seems to be living in the brush pile.
This also explains why the netting wasn't working (I affixed it to the
fence, so she was just running along behind it and jumping into the tomato bed.)
Now that I know what it is I find I'm actually okay with her nibbling in the garden. Kind of funny how that works out...
I've been pulling the tomatoes off the vine early, and while they're a bit smaller, they're ripening up perfectly on the counter inside.
Also got our first squash today!