feat(battle-xp): wire /practice/finish through IBattleXpService

- Practice finish now grants win/loss XP via IBattleXpService.GrantAsync
  with BattleXpMode.Practice. Response fields (get_class_experience,
  class_experience, class_level) reflect post-grant totals.
- Uses req.ClassId from wire; no BattleContext lookup needed.
- Test asserts default XpPerWin=100 crosses classexp.csv L1=50 threshold
  → Level=2 + Exp=50 carry, persists to Viewer.Classes.
- Added loss-XP test asserting default XpPerLoss=25 stays under threshold.

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

SVSim.UnitTests/Controllers/PracticeControllerTests.cs

@@ -197,7 +197,7 @@ public class PracticeControllerTests
     }
 
     [Test]
-    public async Task Finish_accepts_any_recovery_data_returns_zero_xp()
+    public async Task Finish_win_grants_class_xp_and_persists_level_up()
     {
         using var factory = new SVSimTestFactory();
         long viewerId = await factory.SeedViewerAsync();
@@ -218,8 +218,44 @@ public class PracticeControllerTests
         Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK), body);
 
         using var doc = JsonDocument.Parse(body);
-        Assert.That(doc.RootElement.GetProperty("get_class_experience").GetInt32(), Is.EqualTo(0));
-        Assert.That(doc.RootElement.GetProperty("class_experience").GetInt32(), Is.EqualTo(0));
+        // BattleXpConfig.XpPerWin default = 100. classexp.csv seeds L1=50, L2=150, so 100 XP
+        // crosses L1's threshold: land at Level=2 with 50 carry.
+        Assert.That(doc.RootElement.GetProperty("get_class_experience").GetInt32(), Is.EqualTo(100));
+        Assert.That(doc.RootElement.GetProperty("class_experience").GetInt32(), Is.EqualTo(50));
+        Assert.That(doc.RootElement.GetProperty("class_level").GetInt32(), Is.EqualTo(2));
         Assert.That(doc.RootElement.GetProperty("reward_list").GetArrayLength(), Is.EqualTo(0));
+
+        // Persistence check — reload viewer and confirm the ViewerClassData row moved.
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var v = await db.Viewers.Include(x => x.Classes).ThenInclude(c => c.Class)
+            .FirstAsync(x => x.Id == viewerId);
+        var cls1 = v.Classes.Single(c => c.Class.Id == 1);
+        Assert.That(cls1.Level, Is.EqualTo(2));
+        Assert.That(cls1.Exp, Is.EqualTo(50));
+    }
+
+    [Test]
+    public async Task Finish_loss_grants_default_loss_xp()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var finishJson =
+            """{"viewer_id":"0","steam_id":0,"steam_session_ticket":"","deck_no":1,"is_win":0,"evolve_count":0,"total_turn":3,"enemy_class_id":3,"difficulty":1,"deck_format":1,"class_id":1,"recovery_data":"{}"}""";
+
+        var response = await client.PostAsync("/practice/finish",
+            new StringContent(finishJson, Encoding.UTF8, "application/json"));
+
+        var body = await response.Content.ReadAsStringAsync();
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK), body);
+
+        using var doc = JsonDocument.Parse(body);
+        // BattleXpConfig.XpPerLoss default = 25. classexp.csv seeds L1=50, so 25 XP stays
+        // under threshold: Level=1, Exp=25.
+        Assert.That(doc.RootElement.GetProperty("get_class_experience").GetInt32(), Is.EqualTo(25));
+        Assert.That(doc.RootElement.GetProperty("class_experience").GetInt32(), Is.EqualTo(25));
+        Assert.That(doc.RootElement.GetProperty("class_level").GetInt32(), Is.EqualTo(1));
     }
 }