Refreshed workbench navigation and tab experience

The workbench has a redesigned shell, catalog, admin area, dialogs, and help surfaces built on the shared OpenLegacy kit. The tab workspace now lives under the catalog so users stay in context when opening assets, and each tab has its own close control with clearer loading states. [[product:ol-coreiq|OL CoreIQ]] also moves global actions such as theme selection and progress into more predictable locations.