* Auto-attach pasted GitHub PR/issue URLs in the composer
Paste a GitHub PR or issue link into any composer and it shows up
as an attachment pill within a debounce tick when the URL matches
the workspace's remote. On the new-workspace screen, an attached PR
also surfaces an inline "Check out PR #N?" hint next to the picker;
one click promotes it to the checkout target through the same
syncPickerPrAttachment flow the dropdown uses.
Unifies the new-workspace picker and composer attachment picker on
one shared GitHub search hook and cache key, so both consumers (and
the auto-attach lookup) share the React Query cache.
* Fix oxfmt formatting in new-workspace-screen import
