feat(battle-xp): wire story first-clear /finish through IBattleXpService

- StoryConfig.ClassXpPerClear retired; equivalent knob moves to
  BattleXpConfig.StoryXpPerClear (falls back to XpPerWin when null).
- StoryService.FinishAsync now grants class XP via IBattleXpService with
  BattleXpMode.Story on the firstClear && isPlayShape branch. Persists
  post-grant Level/Exp to Viewer.Classes.
- Wire fields (get_class_experience, class_level) stringified as before.
- StoryConfig kept as an empty [ConfigSection] for future story-specific
  knobs. StoryServiceTests updated to reflect the new default path
  (XpPerWin=100 crosses classexp.csv L1=50 → L2 with 50 carry).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.UnitTests/Story/StoryServiceTests.cs

@@ -43,6 +43,8 @@ public class StoryServiceTests
             configService: StoryServiceTestHelpers.NewConfigService(),
             deckRepository: new Mock<SVSim.Database.Repositories.Deck.IDeckRepository>().Object,
             buildDecks: new Mock<SVSim.Database.Repositories.BuildDeck.IBuildDeckRepository>().Object,
+            viewers: new Mock<SVSim.Database.Repositories.Viewer.IViewerRepository>().Object,
+            xp: new Mock<SVSim.Database.Services.BattleXp.IBattleXpService>().Object,
             logger: NullLogger<StoryService>.Instance);
     }
 
@@ -81,6 +83,8 @@ public class StoryServiceTests
             configService: StoryServiceTestHelpers.NewConfigService(),
             deckRepository: new Mock<SVSim.Database.Repositories.Deck.IDeckRepository>().Object,
             buildDecks: new Mock<SVSim.Database.Repositories.BuildDeck.IBuildDeckRepository>().Object,
+            viewers: scope.ServiceProvider.GetRequiredService<SVSim.Database.Repositories.Viewer.IViewerRepository>(),
+            xp: scope.ServiceProvider.GetRequiredService<SVSim.Database.Services.BattleXp.IBattleXpService>(),
             logger: NullLogger<StoryService>.Instance);
     }
 
@@ -414,6 +418,8 @@ public class StoryServiceTests
             configService: StoryServiceTestHelpers.NewConfigService(),
             deckRepository: new Mock<SVSim.Database.Repositories.Deck.IDeckRepository>().Object,
             buildDecks: new Mock<SVSim.Database.Repositories.BuildDeck.IBuildDeckRepository>().Object,
+            viewers: new Mock<SVSim.Database.Repositories.Viewer.IViewerRepository>().Object,
+            xp: new Mock<SVSim.Database.Services.BattleXp.IBattleXpService>().Object,
             logger: NullLogger<StoryService>.Instance);
     }
 
@@ -624,14 +630,26 @@ public class StoryServiceTests
             // Viewer started at RedEther=0; grant of 100 → post-state total = 100.
             Assert.That(resp.RewardList, Has.Count.EqualTo(1));
             Assert.That(resp.RewardList[0].RewardNum, Is.EqualTo("100"));
-            Assert.That(resp.GetClassExperience, Is.EqualTo("200"));
+            // Story XP resolves via DI-registered IBattleXpService → real IGameConfigService
+            // (the local NewConfigService mock is passed to StoryService but the XP service
+            // pulls its own config from DI). BattleXpConfig.ShippedDefaults(): XpPerWin=100,
+            // StoryXpPerClear=null → falls back to XpPerWin=100. Curve L1=50, so 100 XP
+            // → L2 with 50 carry.
+            Assert.That(resp.GetClassExperience, Is.EqualTo("100"));
+            Assert.That(resp.ClassExperience, Is.EqualTo(50));
+            Assert.That(resp.ClassLevel, Is.EqualTo("2"));
             _viewer.Verify(v => v.UpsertProgressAsync(viewerId, 100, true, null), Times.Once);
 
-            // Confirm currency persisted: fetch fresh viewer from a new scope.
+            // Confirm currency + class XP persisted: fetch fresh viewer from a new scope.
             using var verifyScope = factory.Services.CreateScope();
             var db2 = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
-            var freshViewer = await db2.Viewers.FirstAsync(v => v.Id == viewerId);
+            var freshViewer = await db2.Viewers
+                .Include(v => v.Classes).ThenInclude(c => c.Class)
+                .FirstAsync(v => v.Id == viewerId);
             Assert.That(freshViewer.Currency.RedEther, Is.EqualTo(100UL));
+            var cls2 = freshViewer.Classes.Single(c => c.Class.Id == 2);
+            Assert.That(cls2.Level, Is.EqualTo(2));
+            Assert.That(cls2.Exp, Is.EqualTo(50));
         }
     }
 
@@ -828,7 +846,7 @@ internal static class StoryServiceTestHelpers
     {
         var mock = new Mock<SVSim.Database.Services.IGameConfigService>();
         mock.Setup(s => s.Get<SVSim.Database.Models.Config.StoryConfig>())
-            .Returns(new SVSim.Database.Models.Config.StoryConfig { ClassXpPerClear = 200 });
+            .Returns(new SVSim.Database.Models.Config.StoryConfig());
         return mock.Object;
     }