feat(battle-node): cross-side gift + Echo-frame token mining

Close the two generated-token gaps that desynced PvP live test #3 (the
Forestcraft Fairy), both sourced from the 2026-06-03 decomp-validation table.

- MineAddOps now returns (idx, cardId, isSelf) and no longer drops isSelf:0.
  isSelf is the sender's perspective tag on CardObj.IsPlayer (RegisterToken.cs:22)
  and a card has one CardObj.Index, so an isSelf:0 add is the opponent's card.
- New shared BattleSessionState.RecordTokensFrom routes isSelf:1 -> sender,
  isSelf:0 -> opponent (the gift lives in the recipient's map, consulted when
  they play it). PlayActionsHandler delegates to it.
- EchoHandler now mines via the same helper but still returns no routes. An
  Echo's orderList carries the same add-op shape as a send (MakeEchoData ->
  MakeCommonSendAndEchoCardData), so MineAddOps applies verbatim; mining != relaying.

Choice/copy/private-group adds stay skipped (no concrete cardId). Full solution
963/963 green.

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

SVSim.BattleNode/Sessions/Dispatch/BattleSessionState.cs

@@ -41,4 +41,19 @@ internal sealed class BattleSessionState
         GetOrSeedDeckMap(side);            // ensure the per-side map exists (deck-seeded)
         IdxToCardId[side][idx] = cardId;   // overwrite-on-conflict: latest identity wins
     }
+
+    /// <summary>Mine generated-token identities from a sender's <c>orderList</c> <c>add</c> ops and
+    /// record each into the correct side's map. <c>isSelf:1</c> → the sender's own token (<paramref
+    /// name="from"/>); <c>isSelf:0</c> → a cross-side gift living at that idx in the OPPONENT's index
+    /// space (<paramref name="other"/>) — <c>isSelf</c> is the sender's perspective tag on
+    /// <c>CardObj.IsPlayer</c> (RegisterToken.cs:22), and a card has a single <c>CardObj.Index</c>, so
+    /// the gifted idx is the same slot in the recipient's own map (the one consulted when the recipient
+    /// later plays it). Shared by <c>PlayActionsHandler</c> and <c>EchoHandler</c> — an Echo's orderList
+    /// carries the same add-op shape (<c>SendCardDataMaker.MakeEchoData</c>), so both mine identically;
+    /// Echo is mined but never relayed.</summary>
+    public void RecordTokensFrom(IBattleParticipant from, IBattleParticipant other, object? orderList)
+    {
+        foreach (var (idx, cardId, isSelf) in KnownListBuilder.MineAddOps(orderList))
+            RecordToken(isSelf == 1 ? from : other, idx, cardId);
+    }
 }