test(battlenode): capture-replay helper + battle_test fixtures (Phase 2 N1)

CaptureReplay normalizes the capture's send/receive envelope asymmetry (send
frames carry uri at top level + bare payload body; receive frames carry a full
envelope body) and extracts selfDeck + master seed from Matched.

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

SVSim.BattleEngine.Tests/SessionEngine/CaptureReplayTests.cs

@@ -0,0 +1,27 @@
+using System.Linq;
+using NUnit.Framework;
+
+namespace SVSim.BattleEngine.Tests.SessionEngine
+{
+    [TestFixture]
+    public class CaptureReplayTests
+    {
+        [Test]
+        public void Load_parses_frames_and_extracts_self_deck()
+        {
+            var frames = CaptureReplay.Load("battle_test_cl1.ndjson");
+            Assert.That(frames, Is.Not.Empty);
+
+            var deck = CaptureReplay.SelfDeckFrom(frames);
+            Assert.That(deck, Is.Not.Empty, "Matched.selfDeck should parse");
+            Assert.That(deck.Count, Is.EqualTo(40), "a standard deck is 40 cards");
+
+            // Send PlayActions carry their URI at the top level (body.uri == None); the helper must
+            // resolve it correctly, not drop it to None.
+            Assert.That(frames.Any(f => f.Direction == "send" && f.Uri == "PlayActions"),
+                Is.True, "send PlayActions URI resolved from top level");
+
+            Assert.That(CaptureReplay.SeedFrom(frames), Is.GreaterThan(0), "Matched.selfInfo.seed parsed");
+        }
+    }
+}