fix(jetbrains): warn when a provider ends a response unfinished

A turn whose provider ended the stream without a terminal stop reason closed as
"completed" with no message error and no session error, so the session simply went
idle and the truncated answer had no explanation.

Plumb the assistant finish reason through to the frontend and render a warning
outcome card for "unknown" and "other", with the raw reason on the icon tooltip.
The notice is seeded from history so it survives reopening the session. "length" is
excluded because the CLI already writes a visible warning text part for it.

Also broaden the branch/changes refresh from Idle to any non-busy state, so a turn
that edited files still refreshes the git indicators when it ends incomplete, failed,
interrupted, or in error.