Every click within ten milliseconds: a local-first UI

The user’s targets of 2026-10-07 (PLAN.md, “USER TARGETS (2026-10-07, UI)”):

No screen waits on data. At most 10 ms of main-thread work for 100% of clicks (click → handler → state → DOM commit), in every part of the page. The paint on the next frame is reported, not promised.
A local-first UI. A client replica is kept current by the one server stream; reads and writes are local and synchronous; confirmation happens in the background with explicit reconciliation; no click path shows a spinner.
One UI package. The desktop app and the web UI share the same UI code. App-only features live in a separate capability layer, and a guard refuses duplicated UI code.