feat(app,android,ios): search across episodes and people

A search now also finds, with posters and descriptions on, the directors
and studios and the genres whose names hold it, as chips that open their
page, and the episodes whose provider names hold it, which play from the
result (pstr_core::discover::find). The titles it found follow under
their own heading.

The last eight searches are kept in recent-searches.json on this device
only (pstr_core::recent), written only when a search led somewhere, and
offered under the empty search box with a way to clear them. The bridge
exposes search_extras, recent_searches, remember_search and
forget_searches.

On Android and iOS the library's titles are now the whole library
whatever is searched for; the grid narrows through the arrangement, as
it already did. A title opened from an episode result can then always be
shown, and History and Downloads no longer shrink to the search.

ios/ProtonStream/App/ProtonStreamApp.swift

@@ -232,14 +232,26 @@ struct RootView: View {
                 )
             } else {
                 LibraryView(
-                    onResume: play,
-                    onTitle: open,
+                    // A search that led somewhere is one worth offering again.
+                    onResume: { title, index in
+                        model.rememberSearch()
+                        play(title, index)
+                    },
+                    onTitle: { title in
+                        model.rememberSearch()
+                        open(title)
+                    },
                     // The form as a pasted link opens it, only with nothing in it.
                     onAddShare: {
                         incomingLink = ""
                         destination = .shares
                     },
-                    onOpenSettings: { select(.settings) }
+                    onOpenSettings: { select(.settings) },
+                    onBrowse: { facet in
+                        model.rememberSearch()
+                        browsing = facet
+                        browseFrom = nil
+                    }
                 )
             }
         }