feat(tk2): weighted-group reward picking

Replaces the all-rows-granted reward model with per-group weighted
pick. Each ArenaTwoPickReward row now belongs to a RewardGroup with a
Weight; finish/retire groups the WinCount's rows by RewardGroup and
picks exactly one row per group, weighted by Weight (excluding
Weight==0). A RewardNum==0 outcome skips both the grant and the
rewards[] emission. Empty WinCount catalogs emit empty arrays.

Existing seed entries preserve deterministic behavior by living in
single-option groups (each with weight 1). Future seasons can expand
groups to multi-option for true randomized rewards (e.g. 200-280
rupies).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.Database/Migrations/20260531174101_AddArenaTwoPickRewardGroupAndWeight.cs

@@ -0,0 +1,60 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace SVSim.Database.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddArenaTwoPickRewardGroupAndWeight : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_ArenaTwoPickRewards_WinCount_RewardType_RewardId",
+                table: "ArenaTwoPickRewards");
+
+            migrationBuilder.AddColumn<int>(
+                name: "RewardGroup",
+                table: "ArenaTwoPickRewards",
+                type: "integer",
+                nullable: false,
+                defaultValue: 0);
+
+            migrationBuilder.AddColumn<int>(
+                name: "Weight",
+                table: "ArenaTwoPickRewards",
+                type: "integer",
+                nullable: false,
+                defaultValue: 0);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_ArenaTwoPickRewards_WinCount_RewardGroup_RewardType_RewardI~",
+                table: "ArenaTwoPickRewards",
+                columns: new[] { "WinCount", "RewardGroup", "RewardType", "RewardId", "RewardNum" },
+                unique: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_ArenaTwoPickRewards_WinCount_RewardGroup_RewardType_RewardI~",
+                table: "ArenaTwoPickRewards");
+
+            migrationBuilder.DropColumn(
+                name: "RewardGroup",
+                table: "ArenaTwoPickRewards");
+
+            migrationBuilder.DropColumn(
+                name: "Weight",
+                table: "ArenaTwoPickRewards");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_ArenaTwoPickRewards_WinCount_RewardType_RewardId",
+                table: "ArenaTwoPickRewards",
+                columns: new[] { "WinCount", "RewardType", "RewardId" },
+                unique: true);
+        }
+    }
+}

SVSim.Database/Migrations/SVSimDbContextModelSnapshot.cs

@@ -458,6 +458,9 @@ namespace SVSim.Database.Migrations
 
                     NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
 
+                    b.Property<int>("RewardGroup")
+                        .HasColumnType("integer");
+
                     b.Property<long>("RewardId")
                         .HasColumnType("bigint");
 
@@ -467,6 +470,9 @@ namespace SVSim.Database.Migrations
                     b.Property<int>("RewardType")
                         .HasColumnType("integer");
 
+                    b.Property<int>("Weight")
+                        .HasColumnType("integer");
+
                     b.Property<int>("WinCount")
                         .HasColumnType("integer");
 
@@ -474,7 +480,7 @@ namespace SVSim.Database.Migrations
 
                     b.HasIndex("WinCount");
 
-                    b.HasIndex("WinCount", "RewardType", "RewardId")
+                    b.HasIndex("WinCount", "RewardGroup", "RewardType", "RewardId", "RewardNum")
                         .IsUnique();
 
                     b.ToTable("ArenaTwoPickRewards");

SVSim.Database/Models/ArenaTwoPickReward.cs

@@ -10,7 +10,7 @@ namespace SVSim.Database.Models;
 /// <c>SVSim.Bootstrap/Data/seeds/arena-two-pick-rewards.json</c>.
 /// </summary>
 [Index(nameof(WinCount))]
-[Index(nameof(WinCount), nameof(RewardType), nameof(RewardId), IsUnique = true)]
+[Index(nameof(WinCount), nameof(RewardGroup), nameof(RewardType), nameof(RewardId), nameof(RewardNum), IsUnique = true)]
 public class ArenaTwoPickReward
 {
     public long Id { get; set; }
@@ -18,12 +18,24 @@ public class ArenaTwoPickReward
     /// <summary>0..MaxWins. Run ends at LossCount==2 or WinCount==MAX(WinCount).</summary>
     public int WinCount { get; set; }
 
+    /// <summary>
+    /// Groups rows into independent pick buckets. At finish/retire time one row is
+    /// weighted-picked per group. Default 0 keeps legacy rows in a single group.
+    /// </summary>
+    public int RewardGroup { get; set; }
+
+    /// <summary>
+    /// Relative probability weight for this row within its <see cref="RewardGroup"/>.
+    /// Weight == 0 rows are excluded from picking. Default 1.
+    /// </summary>
+    public int Weight { get; set; } = 1;
+
     /// <summary><see cref="UserGoodsType"/> on the wire (e.g. Item=4, Rupy=9).</summary>
     public int RewardType { get; set; }
 
     /// <summary>Item id for Item; 0 for currencies.</summary>
     public long RewardId { get; set; }
 
-    /// <summary>Count (e.g. ticket quantity or rupy amount).</summary>
+    /// <summary>Count (e.g. ticket quantity or rupy amount). 0 = "no reward" outcome.</summary>
     public int RewardNum { get; set; }
 }