* feat(mobile): rename a workspace from the workspace menu
The phone's workspace menu gets a Rename row that swaps the drawer to the
text sheet, prefilled and selected. Saving writes worktree.set displayName at
the row's owner, so server rows work too; an empty name returns the label to
its automatic branch or folder name, as desktop's Workspace details does. A
failed save keeps the sheet and text, shows the host's error and offers Retry.
* refactor: share the automatic workspace name rule with the phone's rename sheet