feat(core,app,android,ios): more like this and browse by genre, studio, person

pstr_core::discover scores every title against another by shared
director, studio, genres, leading tags and format, leaves out its own
franchise and keeps one title per other franchise. It drives a "More
like this" row under a title's episodes and, seeded by the title most
recently watched to the end, a "Because you watched" row on the library
of titles not yet started.

Genre chips on the title page now open a page of every title with that
genre, and the studios and director move from the line of facts onto
chips of their own that do the same. The desktop has a Browse page whose
back link returns to the title; Android and iOS show it over the library
pane. The bridge exposes more_like, browse and facet_kind.

Also moves a doc comment the My List commit left on the wrong function.

docs/METADATA.md

@@ -148,8 +148,19 @@ titles are one director's, and that is not a shelf — and a genre only under 40
 of the library. Four at most, over the unfiltered library. Here: *Directed by
 Satoshi Kon*, *From MADHOUSE*, *From MAPPA*, *From Production I.G*.
 
-**The title page** adds the season, studios, director and next airing episode
-to its line of facts, and the tags beside the genres.
+**The title page** adds the season and next airing episode to its line of
+facts, the tags beside the genres, and the studios and director as chips of
+their own. Each genre, studio and director chip opens a page of every title
+carrying it (`pstr_core::discover::Facet`).
+
+**More like this.** `pstr_core::discover::more_like` scores every other title
+by what it shares with this one — a director 4, a studio 3, a genre 2, one of
+the first eight tags 1, the format 1 on top of anything else — and offers those
+scoring 4 or more: a director, or two genres, but never one genre alone. The
+title's own franchise is left out and each other franchise offers only its best
+match. The same scoring, seeded by the title most recently watched to the end
+and limited to titles not started, is the library's *Because you watched* row.
+No request: it reads only what the match already stored.
 
 **Android.** The same, through the bridge: `AndroidEngine::arrangement`
 returns the grid's tiles and the shelves as keys into `library`'s titles, and