DeleteTaskAsync had no IsConnected guard, unlike every other worker-dependent
command in DetailsIslandViewModel, so an offline delete was a silent no-op.
WorkerClient.DeleteTaskAsync also only caught HubException, letting the
InvalidOperationException thrown by an inactive hub connection escape into
the unobserved command task and vanish.
Gate DeleteTaskCommand behind CanDeleteTask (Task != null && IsConnected),
re-evaluate it on connection-state changes, widen WorkerClient to catch the
connection-inactive case too, and wrap the ViewModel's call in try/catch as
a second line of defense against a race between the guard and the call.
Deleting a child from the details pane hard-deleted straight from the UI
process via TaskRepository, bypassing TaskStateService.TryAdvanceParentAsync
entirely. Deleting the last child of a WaitingForChildren parent that way
left it wedged forever. WorkerHub.DeleteTask now mirrors the MCP delete_task
tool (running-task guard, FK-friendly error, advance-parent call), and the
UI goes through it.
TryAdvanceParentAsync also short-circuited when zero children remained,
treating "no children left" as "nothing to evaluate" instead of "all done" -
removed the early return so an empty child list (vacuously) counts as all
terminal.
mika kuns