* fix(tui): let quit skip an interrupted run's unfinished step
After Ctrl+C the synchronous agent stream keeps running until its next
event. The run was a Textual thread worker, i.e. a thread on asyncio's
default executor, which App.run() joins on shutdown (up to 300 s on
3.12) and interpreter exit joins again with no timeout. Quitting while
a long step was still running therefore hung silently after the
terminal had been restored, and further Ctrl+C presses only printed a
traceback.
Run workers on a daemon thread instead. Quit now waits visibly for
running workers (an interrupted step still checkpoints, a finished run
still saves its title) and refuses sends meanwhile; a second quit
request exits at once. Report unexpected worker exceptions as an error
row and end the run, since Textual no longer catches them.
* docs(changelog): reference #7326 for the TUI quit-after-interrupt fix
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>