feat(android,ios): mark a whole season watched from the title page

Marking was one episode at a time on the title page, or the whole title
from the library's long-press menu, so joining a show at season three
meant ticking every earlier episode. The season row gains a mark button
beside its download one, with an Undo, through a new markEpisodes that
setTitleWatched now uses too. Episodes already in the asked-for state
are left alone, so Undo restores only what changed.

Season chips were keyed by label, and two seasons with one label is a
crash in a lazy list; they are keyed by position now.

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

@@ -551,11 +551,17 @@ class AppViewModel(context: Context, private val workManager: WorkManager) : Vie
      * title's positions are what this throws away, and a mis-tap on a tile's
      * menu should not cost them.
      */
-    fun setTitleWatched(title: TitleRecord, watched: Boolean) {
-        val episodes = title.seasons.flatMap { it.episodes }
+    fun setTitleWatched(title: TitleRecord, watched: Boolean) =
+        markEpisodes(title.seasons.flatMap { it.episodes }, watched, title.displayName)
+
+    /**
+     * Some episodes seen or unseen — a season, or a whole title — with an
+     * Undo; [what] names them in the message.
+     */
+    fun markEpisodes(episodes: List<EpisodeRecord>, watched: Boolean, what: String) {
         changeWatch(
-            episodes,
-            "${title.displayName} marked ${if (watched) "watched" else "unwatched"}",
+            episodes.filter { it.watched != watched },
+            "$what marked ${if (watched) "watched" else "unwatched"}",
         ) { engine, episode, before ->
             val duration = before?.durationSecs
             engine.saveWatchState(

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

@@ -247,6 +247,7 @@ fun ProtonStreamApp(
                                 model::reloadAfterMetadataChange,
                                 model::setWatched,
                                 body,
+                                onMarkEpisodes = model::markEpisodes,
                                 franchise = selected.franchise.mapNotNull { key ->
                                     state.titles.firstOrNull { it.key == key }
                                 },

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

@@ -38,8 +38,10 @@ import androidx.compose.material3.IconButton
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.CheckCircle
 import androidx.compose.material.icons.outlined.CheckCircle
+import androidx.compose.material.icons.filled.DoneAll
 import androidx.compose.material.icons.filled.Download
 import androidx.compose.material.icons.filled.Edit
+import androidx.compose.material.icons.filled.RemoveDone
 import androidx.compose.material.icons.filled.Pause
 import androidx.compose.material.icons.filled.PlayArrow
 import androidx.compose.material.icons.automirrored.filled.ArrowBack
@@ -97,6 +99,8 @@ internal fun TitleScreen(
     onMetadataChanged: () -> Unit,
     onSetWatched: (EpisodeRecord, Boolean) -> Unit,
     padding: PaddingValues,
+    /** Several episodes seen or unseen at once, named for the message. */
+    onMarkEpisodes: (List<EpisodeRecord>, Boolean, String) -> Unit = { _, _, _ -> },
     /** Every title of its franchise, in release order, this one included. */
     franchise: List<TitleRecord> = emptyList(),
     onOpenTitle: (TitleRecord) -> Unit = {},
@@ -343,7 +347,9 @@ internal fun TitleScreen(
                     verticalAlignment = Alignment.CenterVertically,
                 ) {
                     LazyRow(Modifier.weight(1f), horizontalArrangement = Arrangement.spacedBy(8.dp)) {
-                        itemsIndexed(title.seasons, key = { _, it -> it.label }) { index, entry ->
+                        // By position: two seasons can share a label, and a
+                        // repeated key is a crash in a lazy list.
+                        itemsIndexed(title.seasons, key = { index, _ -> index }) { index, entry ->
                             FilterChip(
                                 selected = index == seasonIndex,
                                 onClick = { seasonIndex = index },
@@ -352,6 +358,15 @@ internal fun TitleScreen(
                         }
                     }
                     season?.let {
+                        // For someone joining the show partway, who would
+                        // otherwise tick every earlier episode one by one.
+                        val seen = it.episodes.all(EpisodeRecord::watched)
+                        IconButton(onClick = { onMarkEpisodes(it.episodes, !seen, "${title.displayName} ${it.label}") }) {
+                            Icon(
+                                if (seen) Icons.Default.RemoveDone else Icons.Default.DoneAll,
+                                contentDescription = "Mark ${it.label} ${if (seen) "unwatched" else "watched"}",
+                            )
+                        }
                         IconButton(onClick = { DownloadCoordinator.enqueue(context, it.episodes) }) {
                             Icon(Icons.Default.Download, contentDescription = "Download ${it.label}")
                         }