* fix(app): make new workspace global
New Workspace now opens as an app-wide screen. Host and project context can still preselect the form through query params, but the route itself no longer lives under a host.
* fix(app): simplify new workspace selection
Cmd+N (Ctrl+N off mac) navigates to the new-workspace route through a
global handler keyed on the active host. The sidebar header row surfaces
the shortcut hint on hover, replacing the redundant "+" button that
duplicated the action in the Workspaces section header.