I put the bolt holes in the big lengthwise stretchers today. Those were the final holes to drill.
There was this hunch that I had that the 3/8″ holes I was drilling would be a little too tight for the 3/8″ bolts I was using. This turned out to be correct; the bolts fit, but were not always straight. That was fine; I pulled out the 27/64″ twist drill bit that I bought for just this occasion, chucked it in a brace, and enlarged every hole.
Then there was nothing left to do but test-fit the frame:

Wow, it’s actually starting to look like something now. I tested it for load and everything. Solid. Awesome. There is no discernable lateral racking; you’d hope so due to the extra-wide stretchers.
The next step, I guess, is either to take it apart and prep the surfaces for finishing, or test-fit the top.
PS: Bonus question: What part of this photo is something you wouldn’t usually find in California?