A Test connection listing killed by the shell bound arrives with empty
stdout and exit code 124 or 137, but the settings page dropped the exit
code and modelsReply mapped the empty reply to "format". The user saw
"unexpected format" for a timeout. modelsReply now takes the exit code
and maps 124/137 to "timeout" like generationReply, and the settings
accept path forwards data["exit code"] using the controller's idiom.

Regression: tst_ai_insights modelsReply cases for exits 124/137/1, plus
a settings-harness test feeding exit 124 through the production accept
path. Both fail before (reason "format"), pass after.