Summary Update.

RelayServer/Models/Server/UserRoles.cs

@@ -2,9 +2,21 @@ using SurrealDb.Net.Models;
 
 namespace RelayServer.Models;
 
+/// <summary>
+/// Surreal record for the `user_roles` table. Join table linking users to roles.
+///
+/// Invariant: ServerBootstrapService.SetUserRoleAsync guarantees exactly one row per user.
+/// Multi-role-per-user isn't currently supported by the permission ladder — adding it would
+/// just be a matter of removing the bootstrap's "delete stale rows" step.
+/// </summary>
 public class UserRoles : Record
 {
+    /// <summary>"users:keeper317" — the assignee.</summary>
     public required string UserId { get; set; }
+
+    /// <summary>"roles:abc" — the role being granted.</summary>
     public required string RoleId { get; set; }
+
+    /// <summary>When the assignment was made.</summary>
     public required DateTime AssignedAt { get; set; }
 }