Follow-up to the cloud sessions v2 "Copilot stopped" work, addressing PR
review feedback:
- Add an explicit `default` branch to `isActiveTaskState` so an unknown
task state added server-side returns `true` (active) instead of falling
through to `undefined`. This matches `taskStateToChatSessionStatus`
(unknown -> InProgress) and avoids reintroducing the stuck "Session is
in progress..." spinner when the detail view would otherwise settle
while the session state still reads `in_progress`.
- Remove a stale duplicate comment block in the task history builder.
- Add tests covering `isActiveTaskState`/`isFailedTaskState` across all
states plus the unknown/forward-compat case.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>