handleEvent has no blanket pre-render (removed for issue #4353), so
each handler must explicitly schedule one when it changes something
visible -- every other statusLine.invalidate() call site in this file
pairs it with ui.requestRender(). The new model_changed handler only
invalidated the cache, so an internal model switch (prewalk hand-off,
retry-fallback) while the TUI was otherwise idle left the status line
showing the stale model until an unrelated event happened to render.
Flagged by @chatgpt-codex-connector on PR #6908.
(cherry picked from commit f565e3a4956bda467b6679a3c3f1e48379395a78)