ModelIndexToViewIndex and ViewIndexToModelIndex read conversion arrays
that only renderLines populates. So converting an index before the list
has been rendered ignores the non-model items (e.g. section headers) and
returns a wrong result; the same staleness makes a conversion after the
model has grown index a too-short array and panic (seen in cherry_pick
under -race).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>