feat: replace hex pubkeys with user picture + name in chess cards

In chess note cards (NoteCompose), player hex keys were displayed as
raw strings. Now uses LoadUser + ClickableUserPicture + UsernameDisplay
to show proper profile pictures and display names for:
- Challenge cards (incoming/outgoing)
- Game end cards (both players)
- PGN metadata in game viewers (white/black players)

Added playerContent composable slot to PGNMetadata and ChessGameViewer
so callers can inject platform-specific user rendering.

https://claude.ai/code/session_0171mKrVEfQnNRabmT7Kv4gf

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/chess/ChessGameViewer.kt

@@ -51,11 +51,14 @@ import com.vitorpamplona.quartz.nip64Chess.PGNParser
  *
  * @param pgnContent PGN format string
  * @param modifier Modifier for the viewer
+ * @param playerContent Optional composable to render player names with avatar + display name.
+ *   When provided, PGN player names (which may be hex pubkeys) are rendered using this composable.
  */
 @Composable
 fun ChessGameViewer(
     pgnContent: String,
     modifier: Modifier = Modifier,
+    playerContent: (@Composable (String) -> Unit)? = null,
 ) {
     val gameResult =
         remember(pgnContent) {
@@ -64,7 +67,7 @@ fun ChessGameViewer(
 
     gameResult.fold(
         onSuccess = { game ->
-            ChessGameDisplay(game, modifier)
+            ChessGameDisplay(game, modifier, playerContent)
         },
         onFailure = { error ->
             ChessGameError(
@@ -83,6 +86,7 @@ fun ChessGameViewer(
 private fun ChessGameDisplay(
     game: com.vitorpamplona.quartz.nip64Chess.ChessGame,
     modifier: Modifier = Modifier,
+    playerContent: (@Composable (String) -> Unit)? = null,
 ) {
     var currentMoveIndex by remember { mutableStateOf(0) }
 
@@ -96,7 +100,7 @@ private fun ChessGameDisplay(
             verticalArrangement = Arrangement.spacedBy(12.dp),
         ) {
             // Game metadata header
-            PGNMetadata(game = game)
+            PGNMetadata(game = game, playerContent = playerContent)
 
             // Chess board
             ChessBoard(

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/chess/PGNMetadata.kt

@@ -39,11 +39,15 @@ import com.vitorpamplona.quartz.nip64Chess.ChessGame
  *
  * @param game The chess game with metadata to display
  * @param modifier Modifier for the metadata display
+ * @param playerContent Optional composable to render player names (e.g. with avatar + display name).
+ *   Receives the raw player name string from PGN (which may be a hex pubkey in Nostr context).
+ *   When null, falls back to plain text display.
  */
 @Composable
 fun PGNMetadata(
     game: ChessGame,
     modifier: Modifier = Modifier,
+    playerContent: (@Composable (String) -> Unit)? = null,
 ) {
     Column(
         modifier = modifier.fillMaxWidth(),
@@ -76,12 +80,16 @@ fun PGNMetadata(
                 verticalAlignment = Alignment.CenterVertically,
             ) {
                 game.white?.let { white ->
-                    Text(
-                        text = white,
-                        style = MaterialTheme.typography.bodyMedium,
-                        fontWeight = FontWeight.Medium,
-                        color = MaterialTheme.colorScheme.onSurface,
-                    )
+                    if (playerContent != null) {
+                        playerContent(white)
+                    } else {
+                        Text(
+                            text = white,
+                            style = MaterialTheme.typography.bodyMedium,
+                            fontWeight = FontWeight.Medium,
+                            color = MaterialTheme.colorScheme.onSurface,
+                        )
+                    }
                 }
 
                 Text(
@@ -91,12 +99,16 @@ fun PGNMetadata(
                 )
 
                 game.black?.let { black ->
-                    Text(
-                        text = black,
-                        style = MaterialTheme.typography.bodyMedium,
-                        fontWeight = FontWeight.Medium,
-                        color = MaterialTheme.colorScheme.onSurface,
-                    )
+                    if (playerContent != null) {
+                        playerContent(black)
+                    } else {
+                        Text(
+                            text = black,
+                            style = MaterialTheme.typography.bodyMedium,
+                            fontWeight = FontWeight.Medium,
+                            color = MaterialTheme.colorScheme.onSurface,
+                        )
+                    }
                 }
             }
         }