deleteMessage() bailed at `if (!sessionId) return;`, so the "x" on an output
shown before a model/API was selected did nothing — there's no session yet
(issue #1428). The session id is only needed for the server-side delete; without
one (or with no persisted message ids) we now fall through to removing the DOM,
so the "x" always at least dismisses the bubble.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
