feat: notifications say what changed and alert once: a grouped notice names the tracks, grows without re-alerting, and a phone pile lists its titles (M542 #6146-#6151)

- An update to a grouped notice keeps its arrival time and email state, so the
  phone and the email no longer go off again each time it grows.
- Notices carry the names of what changed (newest ten), shown as three and
  "and N more": tracks still missing after the scan's move/replacement fold,
  duplicate groups new to a sweep, songs merged automatically, and the track
  and listener a playback error was for.
- Duplicates found counts only the groups new to that sweep; playback errors
  count reports, not the unresolved total.
- A scan failure says what stopped and links to Admin > Library.
- Android: a pile of more than three alerts lists the newest five titles.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/notifications/delivery/DeliveryPlan.kt

@@ -30,8 +30,9 @@ internal data class CatchUp(
  * - The mark moves to the newest notice in the page, announced or not, so a
  *   kind with the phone off is never announced later.
  *
- * A coalesced notice (tracks missing, now 5) moves its time forward when its
- * count grows, so it is announced again with the new count.
+ * A coalesced notice (tracks missing, now 5) keeps the time it arrived when
+ * its count grows (M542), so it is announced once: the inbox shows it grown,
+ * the phone does not buzz for it again.
  */
 internal fun planCatchUp(
     page: List<CachedNotificationEntity>,
@@ -51,18 +52,32 @@ internal fun planCatchUp(
 internal sealed interface Announcement {
     data class Each(val items: List<CachedNotificationEntity>) : Announcement
 
-    /** Coming back from a day offline is one line, not forty buzzes. */
-    data class Pile(val count: Int, val channel: ShadeChannel) : Announcement
+    /**
+     * Coming back from a day offline is one line, not forty buzzes. [lines]
+     * are the newest notices' titles, so the pile says what it holds (M542).
+     */
+    data class Pile(
+        val count: Int,
+        val channel: ShadeChannel,
+        val lines: List<String> = emptyList(),
+    ) : Announcement
 }
 
-internal fun announcementFor(fresh: List<CachedNotificationEntity>): Announcement? = when {
-    fresh.isEmpty() -> null
-    fresh.size <= INDIVIDUAL_LIMIT -> Announcement.Each(fresh)
+/** How many titles an expanded pile lists, newest first. */
+internal const val PILE_LINES = 5
+
+internal fun announcementFor(fresh: List<CachedNotificationEntity>): Announcement? {
+    if (fresh.isEmpty()) return null
+    if (fresh.size <= INDIVIDUAL_LIMIT) return Announcement.Each(fresh)
     // A pile goes where its notices would: library health only when every
     // one of them is, so a listener's own news is never filed under it.
-    fresh.all { shadeChannelFor(it.kind) == ShadeChannel.LIBRARY_HEALTH } ->
-        Announcement.Pile(fresh.size, ShadeChannel.LIBRARY_HEALTH)
-    else -> Announcement.Pile(fresh.size, ShadeChannel.YOUR_REQUESTS)
+    val channel = if (fresh.all { shadeChannelFor(it.kind) == ShadeChannel.LIBRARY_HEALTH }) {
+        ShadeChannel.LIBRARY_HEALTH
+    } else {
+        ShadeChannel.YOUR_REQUESTS
+    }
+    val lines = fresh.sortedByDescending { it.createdAt }.take(PILE_LINES).map { it.title }
+    return Announcement.Pile(fresh.size, channel, lines)
 }
 
 /** The phone channel per kind, as the user set it. No settings cached: on, the default for every kind. */
@@ -92,3 +107,7 @@ internal fun deliveryWanted(signedIn: Boolean, enabled: Boolean): Boolean = sign
 
 /** One line for a pile. */
 internal fun pileText(count: Int): String = "$count new notifications"
+
+/** Under an expanded pile's titles: how many it holds beyond them, or null. */
+internal fun pileMore(p: Announcement.Pile): String? =
+    (p.count - p.lines.size).takeIf { it > 0 }?.let { "and $it more" }

android/app/src/main/java/com/fabledsword/minstrel/notifications/delivery/NotificationPoster.kt

@@ -1,6 +1,7 @@
 package com.fabledsword.minstrel.notifications.delivery
 
 import android.annotation.SuppressLint
+import android.app.Notification
 import android.app.NotificationChannel
 import android.app.NotificationManager
 import android.app.PendingIntent
@@ -50,14 +51,20 @@ class NotificationPoster @Inject constructor(
             .setContentIntent(openIntent(item.link, item.id.hashCode()))
             .build()
 
-    private fun pile(p: Announcement.Pile) =
-        NotificationCompat.Builder(context, p.channel.id)
+    /** Collapsed, the count; expanded, the newest titles and how many more. */
+    private fun pile(p: Announcement.Pile): Notification {
+        val style = NotificationCompat.InboxStyle().setBigContentTitle(pileText(p.count))
+        p.lines.forEach { style.addLine(it) }
+        pileMore(p)?.let { style.setSummaryText(it) }
+        return NotificationCompat.Builder(context, p.channel.id)
             .setSmallIcon(R.drawable.ic_notification)
-            .setContentTitle("Minstrel")
-            .setContentText(pileText(p.count))
+            .setContentTitle(pileText(p.count))
+            .setContentText(p.lines.joinToString(" · "))
+            .setStyle(style)
             .setAutoCancel(true)
             .setContentIntent(openIntent(link = null, requestCode = PILE_ID))
             .build()
+    }
 
     /** Each notice gets its own request code, so their links stay apart. */
     private fun openIntent(link: String?, requestCode: Int): PendingIntent =

android/app/src/test/java/com/fabledsword/minstrel/notifications/delivery/DeliveryPlanTest.kt

@@ -99,6 +99,16 @@ class DeliveryPlanTest {
         assertEquals(5, pile.count)
         assertEquals(ShadeChannel.YOUR_REQUESTS, pile.channel)
         assertEquals("5 new notifications", pileText(pile.count))
+        assertEquals(listOf("t-n5", "t-n4", "t-n3", "t-n2", "t-n1"), pile.lines)
+        assertNull(pileMore(pile))
+    }
+
+    @Test
+    fun `a pile names its newest notices and counts the rest`() {
+        val many = (1..17).map { notice("n$it", it.toLong()) }
+        val pile = assertIs<Announcement.Pile>(announcementFor(many))
+        assertEquals(listOf("t-n17", "t-n16", "t-n15", "t-n14", "t-n13"), pile.lines)
+        assertEquals("and 12 more", pileMore(pile))
     }
 
     @Test