fix(worktree): wrap long errors in the New Worktree dialog (#4131)

* fix(worktree): wrap long errors in the New Worktree dialog

A long server error, such as the full path of a worktree that already
holds the branch, could not wrap in the dialog footer. It ran past the
left edge of the dialog and only its tail was readable. The error now
wraps inside the footer next to the buttons, on desktop and mobile.

Fixes #3193

* docs(pr-evidence): add mobile before and after for the New Worktree error