Add player names: settings persistence, replication, screen-space nameplates

- GameSettings: playerName field persisted in Settings.json
- NetworkPlayerSetup: owner-written DisplayName NetworkVariable
  (seeded from settings on spawn, sanitized/truncated, live rename push)
- PlayerNameField: binds the session panel name input to settings
- PlayerNameplates: screen-space overlay labels above players with
  distance-based font scaling (clamped min/max), pooling, FP self-hide

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scripts/Helper/GameSettings.cs

@@ -17,6 +17,7 @@ public static class GameSettings
         public int version = FileVersion;
         public float mouseSensitivity = global::MouseSensitivity.Default;
         public float masterVolume = global::MasterVolume.Default;
+        public string playerName = "";
     }
 
     private static Data _data;
@@ -46,6 +47,19 @@ public static class GameSettings
         }
     }
 
+    /// <summary>Display name shown above the avatar. Empty = per-spawn fallback ("Player &lt;clientId&gt;").</summary>
+    public static string PlayerName
+    {
+        get => Store.playerName ?? "";
+        set
+        {
+            string v = value == null ? "" : value.Trim();
+            if (Store.playerName == v) return;
+            Store.playerName = v;
+            Save();
+        }
+    }
+
     private static Data Load()
     {
         string path = SavePath();