test: ui-regression 'the focused option is highlighted' fails intermittently #608

Reported by the merge lane for #601 (lane ext-601); not reproduced by the lead.

scripts/ui-regression.ts:190, "the focused option is highlighted", failed once in CI on 05b8e1b (a #601 commit that did not touch that code) and passed on the rerun and on later commits. The lane for #519 saw the same assertion fail once earlier, so this is a recurring flake, not a one-off.

Per AGENTS.md a test must not pass by timing luck: the assertion should wait for the exact state it checks (the option's focused/highlighted state after the key event) with a bounded wait rather than read it right after the key.