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/ProtonStreamTests/UiLogicTests.swift

@@ -171,6 +171,18 @@ final class CommonTests: XCTestCase {
         XCTAssertEqual(bare.heading(0), "Episode 4")
     }
 
+    func testThePlayerCaptionsAnEpisodeWithItsNameAndNeverItsFilename() {
+        var named = episode("e")
+        named.providerName = "Dog & Chainsaw"
+        XCTAssertEqual(named.shownName, "Dog & Chainsaw")
+        var bare = episode("e")
+        bare.name = "[Group] Show - S01E01.mkv"
+        bare.detail = bare.name
+        XCTAssertNil(bare.shownName)
+        bare.detail = ""
+        XCTAssertNil(bare.shownName)
+    }
+
     func testEpisodesAreNumberedBySeasonThenByPlaceInTheList() {
         var numbered = episode("e", number: 38)
         numbered.season = 3