fix: resume — save on stop-while-playing, restore to correct track

- Extract saveResumeState helper: saves when playing OR paused (not just
  paused). Both WS and REST stop handlers now call it.
- restoreResume now jumps to saved PlaylistPos before seeking, so the
  correct track is loaded even when playlist order differs.
- Title validation: if the loaded title does not match the window title
  after jumping, abort restore and delete stale resume file.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/server/server.go

@@ -200,14 +200,7 @@ func (s *Server) handleCommand(raw []byte) {
 	case "pause":
 		s.wa.Pause()
 	case "stop":
-		if s.wa.IsPaused() {
-			_ = resume.Save(s.cfg.ResumeFile, resume.State{
-				PlaylistLength: s.wa.GetPlaylistLength(),
-				PlaylistPos:    s.wa.GetPlaylistPosition(),
-				OffsetSeconds:  s.wa.GetPosition(),
-				TrackTitle:     s.wa.GetTitle(),
-			})
-		}
+		s.saveResumeState()
 		s.wa.Stop()
 	case "next":
 		s.wa.NextTrack()
@@ -313,6 +306,25 @@ func (s *Server) killChecker() {
 	}
 }
 
+// saveResumeState persists the current playback position when a track is
+// active (playing or paused). Safe to call unconditionally before Stop.
+func (s *Server) saveResumeState() {
+	state := s.wa.PlayState()
+	if state != 1 && state != 3 { // not playing and not paused
+		return
+	}
+	title := s.wa.GetTitle()
+	if title == "" {
+		return
+	}
+	_ = resume.Save(s.cfg.ResumeFile, resume.State{
+		PlaylistLength: s.wa.GetPlaylistLength(),
+		PlaylistPos:    s.wa.GetPlaylistPosition(),
+		OffsetSeconds:  s.wa.GetPosition(),
+		TrackTitle:     title,
+	})
+}
+
 func (s *Server) restoreResume() {
 	deadline := time.Now().Add(30 * time.Second)
 	for time.Now().Before(deadline) {
@@ -326,14 +338,33 @@ func (s *Server) restoreResume() {
 		return
 	}
 	if s.wa.GetPlaylistLength() != st.PlaylistLength {
+		log.Printf("resume: playlist length mismatch (saved %d, got %d) — aborting",
+			st.PlaylistLength, s.wa.GetPlaylistLength())
 		_ = resume.Delete(s.cfg.ResumeFile)
 		return
 	}
-	s.wa.Play()
+	// Jump to the saved track (JumpToTrack is 0-based, also starts playback).
+	if st.PlaylistPos > 0 {
+		s.wa.JumpToTrack(st.PlaylistPos - 1)
+		time.Sleep(300 * time.Millisecond) // give Winamp a moment to load
+		// Validate title to catch same-length playlists with different content.
+		if st.TrackTitle != "" {
+			if got := s.wa.GetTitle(); got != "" && got != st.TrackTitle {
+				log.Printf("resume: title mismatch (expected %q, got %q) — aborting",
+					st.TrackTitle, got)
+				s.wa.Stop()
+				_ = resume.Delete(s.cfg.ResumeFile)
+				return
+			}
+		}
+	} else {
+		s.wa.Play()
+	}
 	s.wa.Seek(st.OffsetSeconds)
 	s.wa.Pause()
 	_ = resume.Delete(s.cfg.ResumeFile)
-	log.Printf("resume: restored %q at %ds", st.TrackTitle, st.OffsetSeconds)
+	log.Printf("resume: restored %q at %ds (playlist pos %d)",
+		st.TrackTitle, st.OffsetSeconds, st.PlaylistPos)
 }
 
 // ── REST handlers (for curl/debug) ───────────────────────────────────────────
@@ -354,14 +385,7 @@ func (s *Server) handleNext(w http.ResponseWriter, r *http.Request)  { jsonOK(w,
 func (s *Server) handlePrev(w http.ResponseWriter, r *http.Request)  { jsonOK(w, s.wa.PrevTrack()) }
 
 func (s *Server) handleStop(w http.ResponseWriter, r *http.Request) {
-	if s.wa.IsPaused() {
-		_ = resume.Save(s.cfg.ResumeFile, resume.State{
-			PlaylistLength: s.wa.GetPlaylistLength(),
-			PlaylistPos:    s.wa.GetPlaylistPosition(),
-			OffsetSeconds:  s.wa.GetPosition(),
-			TrackTitle:     s.wa.GetTitle(),
-		})
-	}
+	s.saveResumeState()
 	jsonOK(w, s.wa.Stop())
 }