"Add to Watchlist" disappeared from library card menus after the first open, and
the detail-screen bookmark never appeared, for every Plex movie and show (#1873).
Plex Discover's `/library/metadata/matches` answers a `guid` lookup only when
paired with the numeric metadata `type`; a bare guid returns an empty container.
The empty result was cached as "no source can hold this item", hiding the entry
on the next open.
`PlexDiscoverClient.match` now takes the item kind and sends `type=1` (movie) or
`type=2` (show) alongside the guid; other kinds return null without a request.
Fixes#1873
edde746
c5968029e0