With showTaskChatsInCommonFeed enabled, task-planner sessions appear in the
common Direct feed, so /new//clear there hit ChatView's generic intercept and
createSession orphaned the task's planner history behind a fresh session.
Consume the command with a warning toast for task-bound sessions instead.
Also updates 6 stale ChatView.core.test.tsx sendMessage assertions broken by
FN-8502's onDelivered/onFailed options argument.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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