When the main session is aborted while background tasks are running,
notifyParentSession() would attempt to call session.messages() and
session.prompt() on the aborted parent session, causing exceptions
that could crash the TUI.
- Add isAbortedSessionError() helper to detect abort-related errors
- Add abort check in session.messages() catch block with early return
- Add abort check in session.prompt() catch block with early return
- Add test case covering aborted parent session scenario
Fixes TUI crash when aborting main session with running background tasks.
48cb2033e2