Fix test recording keys: rename StartViaJsonString to StartExpanded

The scenario test recording had keys indexed with 'StartViaJsonString'
(the internal variant name) but the test's It block is named
'StartExpanded'. Updated recording keys to match, fixing playback
failure in CI.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Kanchan Joshi