fix album-level tag consistency for mixed-artist tracks

Use album artist overrides during album ripping so compilation-style tracks do not change album performer tags, and add safer disc-number fallbacks for metadata/path generation when providers omit disc fields.

internal/app/app_test.go

@@ -6,6 +6,7 @@ import (
 	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"streamrip-go/internal/audio/tag"
@@ -368,6 +369,51 @@ func TestResolveAllFailedReturnsError(t *testing.T) {
 	}
 }
 
+func TestBuildTagMetadataUsesAlbumArtistOverride(t *testing.T) {
+	meta := map[string]any{
+		"title":        "One Step Too Far",
+		"track_number": float64(15),
+		"performer":    map[string]any{"name": "Faithless"},
+		"artist":       map[string]any{"name": "Faithless"},
+		"album": map[string]any{
+			"id":     "23324600",
+			"title":  "Greatest Hits (Deluxe)",
+			"artist": map[string]any{"name": "Faithless"},
+		},
+	}
+	tags := buildTagMetadata(meta, "One Step Too Far", "tidal", "23324615", ripTrackOptions{albumArtist: "Dido", albumDiscTotal: 2})
+	if tags.AlbumArtist != "Dido" {
+		t.Fatalf("album artist = %q, want Dido", tags.AlbumArtist)
+	}
+	if tags.DiscNumber != 1 {
+		t.Fatalf("disc number = %d, want 1", tags.DiscNumber)
+	}
+	if tags.DiscTotal != 2 {
+		t.Fatalf("disc total = %d, want 2", tags.DiscTotal)
+	}
+}
+
+func TestTrackOutputPathFallsBackToDisc1(t *testing.T) {
+	tmp := t.TempDir()
+	d := config.DefaultConfigData()
+	d.Downloads.Folder = tmp
+	d.Downloads.DiscSubdirectories = true
+	d.Downloads.SourceSubdirectories = false
+	cfg := &config.Config{File: d, Session: d}
+	m := &Main{Config: cfg}
+
+	meta := map[string]any{
+		"title":        "Song",
+		"track_number": float64(1),
+		"performer":    map[string]any{"name": "Dido"},
+		"album":        map[string]any{"id": "a", "title": "Greatest Hits", "artist": map[string]any{"name": "Dido"}},
+	}
+	path := m.trackOutputPath("tidal", "1", "Song", "flac", meta, filepath.Join(tmp, "Album"), 2)
+	if !strings.Contains(path, string(filepath.Separator)+"Disc 1"+string(filepath.Separator)) {
+		t.Fatalf("expected Disc 1 subdir in path, got %q", path)
+	}
+}
+
 func TestPlaylistRipPipeline(t *testing.T) {
 	tmp := t.TempDir()