add a disc icon next to disc titles

Use Icons.Rounded.DiscFull, which is distinct from the album tab's
Icons.Rounded.Album, and only beside a real title rather than the
"Disc N" fallback.

app/src/main/kotlin/com/subtracks/ui/library/AlbumDetailScreen.kt

@@ -1,12 +1,20 @@
 package com.subtracks.ui.library
 
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.rounded.DiscFull
+import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
@@ -119,7 +127,7 @@ fun AlbumDetailScreen(
                 val disc = song.disc ?: 1L
                 val discLabel = discLabels[disc]
                 if (disc != lastDisc && (multiDisc || discLabel != null)) {
-                    item(key = "disc:$disc") { DiscHeader(discLabel ?: "Disc $disc") }
+                    item(key = "disc:$disc") { DiscHeader(discLabel ?: "Disc $disc", showIcon = discLabel != null) }
                 }
                 lastDisc = disc
                 item(key = song.id) {
@@ -137,12 +145,28 @@ fun AlbumDetailScreen(
 }
 
 @Composable
-private fun DiscHeader(text: String) {
-    Text(
-        text = text,
-        style = MaterialTheme.typography.titleMedium,
-        fontWeight = FontWeight.SemiBold,
-        color = MaterialTheme.colorScheme.onSurfaceVariant,
+private fun DiscHeader(
+    text: String,
+    showIcon: Boolean,
+) {
+    Row(
+        verticalAlignment = Alignment.CenterVertically,
         modifier = Modifier.padding(start = 16.dp, end = 16.dp, top = 20.dp, bottom = 4.dp),
-    )
+    ) {
+        if (showIcon) {
+            Icon(
+                imageVector = Icons.Rounded.DiscFull,
+                contentDescription = null,
+                tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.size(16.dp),
+            )
+            Spacer(Modifier.width(8.dp))
+        }
+        Text(
+            text = text,
+            style = MaterialTheme.typography.titleMedium,
+            fontWeight = FontWeight.SemiBold,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+    }
 }