Replace the flat download list with a Downloaded browse surface that
reuses the online grids/cards/detail pages, filtered to on-device media,
plus a demoted Transfers tab. Add repository browse commands
(getDownloadedLibraries/Items, disk usage) with offline/hybrid
implementations, a downloadedCatalog service, formatBytes helper, and
per-item/device disk-usage labels on cards and grids. Regenerated
bindings.
Also carries the inseparable UR-052 offline-filter hunks in
offline.rs/hybrid.rs.
TRACES: UR-055 | DR-081, DR-082, DR-083, DR-084; UR-056 | DR-085