Replace the navigate-away ReleaseArchiveBrowser cards and the redundant top-level Releases
toggle with an in-page MudTabs strip under the Releases mode: ALL (CmsAllReleasesGrid) plus
one enum-driven tab per ReleaseMedium. Sessions/Mixes browsers gain an Embedded flag that
suppresses standalone page chrome when hosted as tab content; CmsCutBrowser is the new
Cut-filtered grid. /tracks/sessions, /tracks/mixes, /tracks/archive stay reachable by URL.
daniel-c-harvey