refactor(battlenode): engine-first token identity (cardId); keep wire-mining fallback (M-HC-4f, partial)

Source the played card's opponent-facing knownList[].cardId off the shadow engine
(SessionBattleEngine.PlayedCardId -> BattleCardBase.CardId), engine-first with the
wire-mined idx->cardId map as the fallback. PROVEN engine-resolved (each backed by a
HeadlessConductorTests PlayedCardId_* test): deck cards and receive-path substituted/
revealed tokens (engine seats the wire id at the wire idx).

PARTIAL retirement: the wire-mining bookkeeping (MineAddOps/MineChoicePicks/MineCopyTokens
+ Record*From) is KEPT as the load-bearing fallback. The choice/Discover, copy/clone and
cross-side (isSelf:0) token cases are NOT proven to resolve at a wire idx headless — the
autonomous token_draw path seats a chosen token at engine Index 0 (would collide with the
leader), and copy/cross-side aren't cheaply fixturable. Deleting their mining on faith
would silently corrupt opponent reveals, so it stays behind a TODO(M-HC-4f) gate.

- SessionBattleEngine.PlayedCardId: new accessor mirroring PlayedCardClan/Tribe.
- BuildPlayedCard: signature deckMap->explicit cardId; null on cardId==0 (no engine id AND
  no mined/deck-map fallback).
- PlayActionsHandler: cardId = engine.PlayedCardId(seat, idx, fallback: mapped) ; mining retained.
- Tests: PlayedCardId_* (deck/substituted/degrade pass; choice-gap [Explicit] documents the
  Index-0 finding). KnownListBuilder + CaptureConformance call-sites updated to new signature.

Full BattleNode suite 263/263 green; HeadlessConductorTests 27/27; drift clean; no Engine edits.

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

SVSim.BattleNode/Sessions/Dispatch/BattleSessionState.cs

@@ -5,10 +5,13 @@ using SVSim.BattleNode.Sessions;
 namespace SVSim.BattleNode.Sessions.Dispatch;
 
 /// <summary>Mutable per-session state shared across frame handlers. The mulligan barrier's
-/// post-swap hands, plus (PvP-equivalency, vanilla slice) the per-side idx->cardId map used to
-/// synthesize the opponent-facing <c>knownList</c>. Generated tokens (cardIds mined from
-/// orderList <c>add</c> ops) are recorded into the SAME
-/// <see cref="IdxToCardId"/> map via <see cref="RecordToken"/>; a reveal-gate set is still future.</summary>
+/// post-swap hands, plus the per-side idx->cardId map used as the FALLBACK identity source for the
+/// opponent-facing <c>knownList</c>. As of M-HC-4f the played card's identity is ENGINE-first — the handler
+/// reads <c>SessionBattleEngine.PlayedCardId</c> and uses this map only as the fallback (non-engine session,
+/// or a token case the engine doesn't resolve at a wire idx). The map still holds deck cards (seeded from the
+/// shuffled deck) and the wire-mined generated/choice/copy/cross-side token identities (recorded via
+/// <see cref="RecordToken"/>) — those token cases remain wire-mined pending an engine-read proof
+/// (TODO(M-HC-4f) in <c>PlayActionsHandler</c>).</summary>
 internal sealed class BattleSessionState
 {
     /// <summary>The one random value chosen per battle. Every per-battle RNG (shared effect seed,