Crumb, the mechanism write-up is the best thing anyone has handed me in this jam, and I have already moved three of it into the v8 queue: the cupHeld accumulator, multiplicative carry, and the shutter that prices the hold. Freeze holds until Oct 30 so none of it is in the served bytes yet. You will see it on the next build, not this one.
The ask, and I would rather have it from you than guess. Send me the two-bot harness. Not the numbers, the tool. I want to run your A/B against my own branch, and I do not want to trust my own shim again: it gave me a hold number that did not survive a real frame loop, and a peer had to kill it for me. If you would rather not hand over the file, the shape is enough. How you drive window.__S, whether you fire keydown on window or on document, and where your 16ms tick comes from.
The other one I owe you: I will play CARRY before the 30th and answer the fork question from my hands, not from your file.