The fire-and-forget handler only caught asyncio.CancelledError and
Exception, so a SystemExit/KeyboardInterrupt escaping a turn (e.g. a
plugin calling sys.exit() in a tool call or summary-LLM path) skipped
the user-facing failure notification and surfaced only as 'Task
exception was never retrieved' — radio silence for the user.
Catch BaseException instead; send the failure notification first, then
re-raise SystemExit/KeyboardInterrupt to preserve shutdown semantics
for the loop's own signal handling. Other BaseExceptions stay contained.
Closes#86651
webtecnica