feat(android): move skip classification from client to server

PlayEventsReporter used to make the skip-vs-ended call client-side:
if the play head reached within 3s of duration -> playEnded with
full duration; otherwise -> playSkipped (forces was_skipped=true on
the server regardless of actual play time). That left the server's
configurable skip rule (skip_max_completion_ratio +
skip_max_duration_played_ms, default 50%/30s) dead code and meant
any "next" tap registered as a skip even after most of the track
played - too strict per operator 2026-06-01.

PlayEventsReporter now always calls playEnded with the actual
position played to. Server's RecordPlayEnded applies the rule and
decides was_skipped. If the play ran to completion, the last
observed position is approximately the track duration -> ratio ~1
-> not skipped. If the user hit next mid-track, the duration the
server sees is the real listen time and the rule fires normally.

Drops the curReachedEnd field and COMPLETION_TOLERANCE_MS constant
that backed the prior classification. playSkipped wire endpoint
stays in place for a future explicit-dislike affordance (not wired
to track-change transitions any more).

Parity-map row updated. Web backflow tracked as task #57 (Scribe
521). Flutter not touched - deprecated per M8.

android/app/src/main/java/com/fabledsword/minstrel/player/PlayEventsReporter.kt

@@ -9,7 +9,6 @@ import com.fabledsword.minstrel.cache.mutations.MutationQueue
 import com.fabledsword.minstrel.cache.mutations.PlayOfflinePayload
 import com.fabledsword.minstrel.di.ApplicationScope
 import com.fabledsword.minstrel.models.wire.PlayEndedRequest
-import com.fabledsword.minstrel.models.wire.PlaySkippedRequest
 import com.fabledsword.minstrel.models.wire.PlayStartedRequest
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
@@ -21,8 +20,6 @@ import java.util.UUID
 import javax.inject.Inject
 import javax.inject.Singleton
 
-private const val COMPLETION_TOLERANCE_MS = 3_000L
-
 /**
  * Mobile play-event lifecycle reporter. Closes the parity gap where
  * Android-played tracks never reached the server — without this,
@@ -31,11 +28,18 @@ private const val COMPLETION_TOLERANCE_MS = 3_000L
  * and system-playlist rotation didn't advance on mobile activity.
  *
  * State machine over (current track id, playing) observed against
- * [PlayerController.uiState]. Mirrors Flutter's
- * `play_events_reporter.dart`. The skip-vs-ended classification uses
- * a 3-second tolerance to avoid marking naturally-finished in-queue
- * tracks as skipped (which would dilute the recommendation
- * skip-ratio).
+ * [PlayerController.uiState]. The client always calls `playEnded`
+ * with the actual position played to; the server applies its
+ * configurable skip rule (`skip_max_completion_ratio` AND
+ * `skip_max_duration_played_ms`, default 50% AND 30s) to decide
+ * was_skipped. Earlier shape made the classification client-side via
+ * a "within 3s of duration" rule, which left the server's threshold
+ * dead code and treated any "next" tap as a skip — too strict
+ * (operator 2026-06-01).
+ *
+ * `playSkipped` endpoint stays on the wire for a future explicit-
+ * dislike affordance, but isn't called from normal track-change
+ * transitions any more.
  *
  * Live calls go through [EventsApi]; failures fall through to the
  * offline [MutationQueue] so a flaky connection never loses a play.
@@ -59,7 +63,6 @@ class PlayEventsReporter @Inject constructor(
     private var curSource: String? = null
     private var curLastPositionMs: Long = 0
     private var curDurationMs: Long = 0
-    private var curReachedEnd: Boolean = false
 
     // Server play_event_id when the live play_started succeeded;
     // null if start failed/offline — then the close is captured into
@@ -106,12 +109,7 @@ class PlayEventsReporter @Inject constructor(
         // change (where currentTrack is briefly the new one).
         if (curTrackId != null && trackId == curTrackId) {
             curLastPositionMs = positionMs
-            if (durationMs > 0) {
-                curDurationMs = durationMs
-                if (positionMs >= curDurationMs - COMPLETION_TOLERANCE_MS) {
-                    curReachedEnd = true
-                }
-            }
+            if (durationMs > 0) curDurationMs = durationMs
         }
 
         prevTrackId = trackId
@@ -123,7 +121,6 @@ class PlayEventsReporter @Inject constructor(
         curSource = source
         curLastPositionMs = 0
         curDurationMs = durationMs
-        curReachedEnd = false
         openPlayEventId = null
         startLive(trackId = trackId, source = source)
     }
@@ -158,30 +155,26 @@ class PlayEventsReporter @Inject constructor(
             resetCurrent()
             return
         }
-        val reached = curReachedEnd
-        val lastPos = curLastPositionMs
-        val durationMs = if (reached && curDurationMs > 0) curDurationMs else lastPos
+        // Always send the actual position played to; the server's
+        // skip rule (50%/30s defaults, configurable) classifies
+        // was_skipped from this. If the track ran to completion the
+        // last observed position is ~= duration, which gives ratio ~1
+        // and the server records a non-skip. The COMPLETION_TOLERANCE
+        // rounding the prior shape did is no longer needed — the
+        // server's threshold is the source of truth.
+        val durationMs = curLastPositionMs
         val source = curSource
         val id = openPlayEventId
 
         if (!viaOffline && id != null) {
             scope.launch {
                 try {
-                    if (reached) {
-                        api.playEnded(
-                            PlayEndedRequest(
-                                playEventId = id,
-                                durationPlayedMs = durationMs,
-                            ),
-                        )
-                    } else {
-                        api.playSkipped(
-                            PlaySkippedRequest(
-                                playEventId = id,
-                                positionMs = lastPos,
-                            ),
-                        )
-                    }
+                    api.playEnded(
+                        PlayEndedRequest(
+                            playEventId = id,
+                            durationPlayedMs = durationMs,
+                        ),
+                    )
                 } catch (
                     @Suppress("TooGenericExceptionCaught", "SwallowedException") e: Throwable,
                 ) {
@@ -200,7 +193,6 @@ class PlayEventsReporter @Inject constructor(
         curSource = null
         curLastPositionMs = 0
         curDurationMs = 0
-        curReachedEnd = false
         openPlayEventId = null
     }