* fix(tui): show picker labels as written instead of parsing markup
SelectScreen passed thread titles and model display names to Textual as
plain str, which Textual parses as content markup. A thread title such as
'Fix [/bold] in parser' raised MarkupError and exited the app whenever
/threads opened, and '[a]' vanished from the list. Wrap the title and
option labels in Rich Text so they render literally.
* docs(changelog): reference #7631 for the TUI picker markup fix
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>