fix(battlenode): PlayedCardTribe degrades to 0 not empty; clan/tribe builder tests (M-HC-4e review)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

SVSim.BattleNode/Sessions/Dispatch/Handlers/PlayActionsHandler.cs

@@ -61,7 +61,7 @@ internal sealed class PlayActionsHandler : IFrameHandler
         // value would miss it). Prod always emits both on every knownList entry: clan as the int ClanType
         // ordinal, tribe as the comma-joined int TribeType string ("0" for none). Same senderSeat mapping.
         int playedClan = ctx.Engine.PlayedCardClan(senderSeat, playIdx, fallback: 0);
-        string playedTribe = ctx.Engine.PlayedCardTribe(senderSeat, playIdx);
+        string playedTribe = ctx.Engine.PlayedCardTribe(senderSeat, playIdx, fallback: "0");
 
         var played = KnownListBuilder.BuildPlayedCard(
             deckMap, playIdx, orderList, cost: playedCost, spellboost: playedSpellboost,

SVSim.BattleNode/Sessions/Engine/SessionBattleEngine.cs

@@ -302,13 +302,18 @@ internal sealed class SessionBattleEngine
     /// <see cref="BattleCardBase.Tribe"/>, whose getter folds in any skill-applied tribe CHANGE/ADD over
     /// <c>BaseParameter.Tribe</c> (and drops ALL when the resolved list has ≥2 entries) — so the wire carries
     /// the LIVE tribe, the faithful value over the static card-master one.
-    /// <para>Same post-resolution zone search as <see cref="PlayedCardCost"/>; no engine / no card → "" (an
-    /// engine that isn't owned this session emits no card, so the caller's BuildPlayedCard never fires).</para></summary>
-    public string PlayedCardTribe(bool playerSeat, int idx)
+    /// <para>Same post-resolution zone search + degrade-to-<paramref name="fallback"/> contract as
+    /// <see cref="PlayedCardClan"/>: no engine / no card → <paramref name="fallback"/> (default <c>"0"</c>, the
+    /// prod no-tribe form — NEVER empty, which is wire-illegal: prod always sends tribe as a non-empty string,
+    /// the client reads it via <c>item.Value.ToString()</c> at NetworkBattleReceiver.cs:2382). The degrade is
+    /// LIVE, not dead: a second concurrent battle that loses the single-active-engine gate has <c>_mgr is null</c>
+    /// yet still emits a knownList entry (KnownListBuilder.BuildPlayedCard gates on the deck map, not engine
+    /// ownership), so this path must hand back a legal wire value.</para></summary>
+    public string PlayedCardTribe(bool playerSeat, int idx, string fallback = "0")
     {
-        if (_mgr is null) return string.Empty;
+        if (_mgr is null) return fallback;
         var card = FindByIndex(Seat(playerSeat), idx);
-        if (card is null) return string.Empty;
+        if (card is null) return fallback;
         var tribe = card.Tribe;
         // Prod's no-tribe form is the single "0" (TribeType.ALL == 0), never an empty string; an empty list
         // (defensive) renders the same "0".

SVSim.UnitTests/BattleNode/Sessions/KnownListBuilderTests.cs

@@ -125,6 +125,33 @@ public class KnownListBuilderTests
         Assert.That(KnownListBuilder.BuildPlayedCard(deckMap, 3, OrderListMove(3, 10, 20))!.Spellboost, Is.EqualTo(0));
     }
 
+    [Test]
+    public void BuildPlayedCard_emits_clan_tribe_passed_by_caller()
+    {
+        // M-HC-4e: the handler reads the engine-resolved clan/tribe
+        // (SessionBattleEngine.PlayedCardClan / PlayedCardTribe) and passes them in; BuildPlayedCard lands
+        // them on the entry verbatim. (A wrong clan/tribe yields a different field — non-vacuity.)
+        var deckMap = new Dictionary<int, long> { [3] = 101314020L };
+        var entry = KnownListBuilder.BuildPlayedCard(
+            deckMap, playIdx: 3, orderList: OrderListMove(3, 10, 20), cost: 3, spellboost: 2, clan: 8, tribe: "7,16");
+        Assert.That(entry, Is.Not.Null);
+        Assert.That(entry!.Clan, Is.EqualTo(8));
+        Assert.That(entry.Tribe, Is.EqualTo("7,16"));
+    }
+
+    [Test]
+    public void BuildPlayedCard_defaults_clan_to_zero_and_tribe_to_string_zero_when_caller_passes_none()
+    {
+        // A play whose engine read degraded (single-active-engine gate: _mgr null → the accessor fallback)
+        // emits clan 0 (ClanType.ALL ordinal) and tribe "0" (the prod no-tribe form, NEVER empty —
+        // empty is wire-illegal). The param defaults match the accessor fallbacks.
+        var deckMap = new Dictionary<int, long> { [3] = 101311010L };
+        var entry = KnownListBuilder.BuildPlayedCard(deckMap, 3, OrderListMove(3, 10, 20));
+        Assert.That(entry, Is.Not.Null);
+        Assert.That(entry!.Clan, Is.EqualTo(0));
+        Assert.That(entry.Tribe, Is.EqualTo("0"));
+    }
+
     [Test]
     public void RenameTargets_passes_isSelf_through_verbatim()
     {