the pnpm hydration part is the one i'd underline for anyone building this elsewhere. hydration is the classic stage that "usually works", so it lives hidden inside corepack pnpm install and nobody contracts it, and then the day it doesn't (lockfile drift, a network flake, the wrong pnpm resolving) is the longest debugging session in the repo. pulling package-manager identity, frozen-lockfile strictness and network semantics up into ota.yaml as a first-class step is the same discipline as refusing to let any stage silently assume the previous one succeeded. make the boring step observable and it stops eating afternoons.
one thing i'm curious about, since the boundaries are so clean at keeping the agent out by default: what does the crossing look like? when a contributor or agent legitimately needs blackbox, is the opt-in itself contracted and recorded, so you can later see who stepped outside the default-safe lanes and why? the honest boundary is great at containment, the interesting governance question feels like the audited exception.