Make the inline title lighter and the only way to rename

Claim the title edit during the workspace's first render so a new
document's field is focused as soon as it mounts. Sidebar Rename now
opens the document and its inline title instead of a modal, which is
removed. Editing keeps the resting box and ink on a selected wash with a
hairline ring, a duplicate title gets sentence-case guidance, and leaving
a rejected title reverts it instead of retrying.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>