feat(core,app,android,ios): finish adding a first share where it pays off

- A link with a password of its own, added without one, now fails as
  "This link has a password of its own" instead of the handshake's
  refusal. The link's public flags are only asked for after a refusal.
  The desktop form turns its password toggle on.
- After the first share is added, all three clients go to the library.
  While that share is being listed, the empty library says so instead of
  offering to add a share.
- The desktop library offers posters and synopses once there is a
  library to put them on. The offer says what is sent, links to
  Settings, never turns anything on, and "Not now" is remembered.

android/app/src/main/java/io/narl/protonstream/ui/LibraryScreen.kt

@@ -188,6 +188,12 @@ internal fun LibraryScreen(
                     "Nothing matches",
                     "No title in the library is called “${state.query.trim()}”.",
                 )
+                // A share just added: say it is being looked through, rather
+                // than offer to add the one that is already filling the page.
+                state.titles.isEmpty() && state.activity != null -> EmptyState(
+                    "Looking through the share",
+                    "${state.activity} Its titles appear here once it has been listed.",
+                )
                 state.titles.isEmpty() -> EmptyState(
                     "Your library is empty",
                     "Add a Proton Drive share link, and everything playable behind it shows up here.",

android/app/src/main/java/io/narl/protonstream/ui/ProtonStreamApp.kt

@@ -279,7 +279,14 @@ fun ProtonStreamApp(
                     }
                     Destination.Shares -> SharesScreen(
                         state.shares,
-                        model::addShare,
+                        { name, url, password ->
+                            // The first share is the library: watch it fill
+                            // rather than stay on a form that has done its job.
+                            val first = state.titles.isEmpty()
+                            model.addShare(name, url, password).also { refusal ->
+                                if (refusal == null && first) destination = Destination.Library
+                            }
+                        },
                         model::repairShare,
                         model::refreshShare,
                         model::removeShare,