The app already holds the box the document reported, so the refit and
the fit pass await the init's ready and call `handle.fitDimensions`
instead of posting `measure` and waiting on `measure-result`. The
document's measure, its retries, and the measure promise and timeout go.
The document still resizes locally on a text-size change, so every grid
the app sends (init, resize, reflow) carries the laid-out frame it was
fitted to. `holdSubscribedGrid` replaces `subscribeFitDimensions`, so
the only fits are `fitDimensionsFromCell` and `handle.fitDimensions`.
The render rig reads its fit from the ready box. The recorder adapter
mounts the new handle with the same recorded effects; the goldens it
mounts move on their adapterSha256 header only.
Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb
Jinwoo-H
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