fix(android,ios): the player names the episode, not its file

The header under the episode's numbering showed `Episode::detail`, which
falls back to the file name — `[Judas] Chainsaw Man - S01E01.mkv` on a
phone, where the desktop shows `Dog & Chainsaw`. It now shows the
provider's name for the episode, else the one the file name gave it, and
nothing rather than the file name: the release group's tag is no caption,
and it is what a screenshot of the player would carry away.

ios/ProtonStream/Player/PlayerView.swift

@@ -210,7 +210,9 @@ struct PlayerView: View {
             // thing a viewer who has just woken the controls is checking.
             VStack(alignment: .leading, spacing: 0) {
                 Text(host.episode?.label ?? "").textStyle(.titleMedium).foregroundStyle(.white).lineLimit(1)
-                Text([host.title?.displayName, host.episode?.detail].compactMap { $0 }.filter { !$0.isEmpty }.joined(separator: "  •  "))
+                // The episode's name, never its file name: a release group's
+                // tag is no caption, and it is what a screenshot would carry away.
+                Text([host.title?.displayName, host.episode?.shownName].compactMap { $0 }.filter { !$0.isEmpty }.joined(separator: "  •  "))
                     .textStyle(.bodySmall).foregroundStyle(.white.opacity(0.7)).lineLimit(1)
             }
             .frame(maxWidth: .infinity, alignment: .leading)

ios/ProtonStream/UI/Common.swift

@@ -342,12 +342,19 @@ func downloadStatusLine(_ download: RetainedDownload, waitingFor: String? = nil)
 }
 
 extension EpisodeRecord {
+    /// The episode's own name: the provider's, else the one the filename gave
+    /// it. `nil` rather than the filename, which is a release group's tag and
+    /// the episode's numbering again.
+    var shownName: String? {
+        providerName ?? (detail != name && !detail.isEmpty ? detail : nil)
+    }
+
     /// What an episode row is headed with: "1. Mother and Children".
     ///
     /// The provider's name for the episode, else the name the filename gave it,
     /// else "Episode 1". The bare filename only when none of those exist.
     func heading(_ position: Int) -> String {
-        let named = providerName ?? (detail != name ? detail : nil)
+        let named = shownName
         switch (named, number) {
         case let (named?, number?): return "\(number). \(named)"
         case let (named?, nil): return named