feat(battle-xp): BattleXpGrantResult carries LeveledUp signal

BattleXpGrantResult gains a LeveledUp bool set true iff at least one curve
threshold was crossed during the grant (comparing pre-Level to post-Level after
the level-up loop). Callers will gate class_level_up mission emits on this flag
rather than caching pre-state themselves.

No behavior change for existing callers — they read GetXp/TotalXp/Level today
and never check LeveledUp yet. Tests cover: unchanged level → false, single
threshold → true, multi-threshold within one grant → still true, unknown class
guardrail → false.

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

SVSim.Database/Services/BattleXp/BattleXpService.cs

@@ -30,7 +30,7 @@ public sealed class BattleXpService : IBattleXpService
             _log.LogWarning(
                 "BattleXpService: viewer {ViewerId} has no ViewerClassData for classId {ClassId}; skipping grant.",
                 viewer.Id, classId);
-            return new BattleXpGrantResult(0, 0, 1);
+            return new BattleXpGrantResult(0, 0, 1, LeveledUp: false);
         }
 
         int amount = ResolveAmount(mode, isWin);
@@ -42,6 +42,7 @@ public sealed class BattleXpService : IBattleXpService
         var byLevel = curve.ToDictionary(e => e.Id, e => e.NecessaryExp);
         int maxLevel = curve.Count == 0 ? row.Level : curve.Max(e => e.Id);
 
+        int startingLevel = row.Level;
         while (row.Level < maxLevel
                && byLevel.TryGetValue(row.Level, out var needed)
                && row.Exp >= needed)
@@ -50,7 +51,7 @@ public sealed class BattleXpService : IBattleXpService
             row.Level += 1;
         }
 
-        return new BattleXpGrantResult(amount, row.Exp, row.Level);
+        return new BattleXpGrantResult(amount, row.Exp, row.Level, LeveledUp: row.Level > startingLevel);
     }
 
     private int ResolveAmount(BattleXpMode mode, bool isWin)

SVSim.Database/Services/BattleXp/IBattleXpService.cs

@@ -6,8 +6,11 @@ namespace SVSim.Database.Services.BattleXp;
 /// Amounts returned to callers after a class-XP grant. <see cref="TotalXp"/> and
 /// <see cref="Level"/> are POST-grant, POST-level-up (matching the wire shape's
 /// <c>class_experience</c> + <c>class_level</c> post-state semantics).
+/// <see cref="LeveledUp"/> is <c>true</c> iff at least one level threshold was
+/// crossed during this grant — callers gate <c>class_level_up</c> mission emits
+/// on this flag rather than caching pre-state themselves.
 /// </summary>
-public sealed record BattleXpGrantResult(int GetXp, int TotalXp, int Level);
+public sealed record BattleXpGrantResult(int GetXp, int TotalXp, int Level, bool LeveledUp);
 
 public interface IBattleXpService
 {

SVSim.UnitTests/Services/BattleXpServiceTests.cs

@@ -185,7 +185,49 @@ public class BattleXpServiceTests
         Assert.That(r.GetXp, Is.EqualTo(0));
         Assert.That(r.TotalXp, Is.EqualTo(0));
         Assert.That(r.Level, Is.EqualTo(1));
+        Assert.That(r.LeveledUp, Is.False);
         Assert.That(v.Classes.Single().Exp, Is.EqualTo(0),
             "Class 1's row must not have been touched.");
     }
+
+    // ---- LeveledUp signal ----
+
+    [Test]
+    public async Task LeveledUp_is_false_when_grant_stays_within_same_level()
+    {
+        // L1 requires 100 to reach L2; grant only 40.
+        var svc = NewService(new BattleXpConfig { XpPerWin = 40 });
+        var v = NewViewerWithClass(1);
+
+        var r = await svc.GrantAsync(v, 1, isWin: true, BattleXpMode.Rank);
+
+        Assert.That(r.Level, Is.EqualTo(1));
+        Assert.That(r.LeveledUp, Is.False);
+    }
+
+    [Test]
+    public async Task LeveledUp_is_true_when_grant_crosses_a_threshold()
+    {
+        // L1=100 → grant 130 → L2 with 30 carry.
+        var svc = NewService(new BattleXpConfig { XpPerWin = 130 });
+        var v = NewViewerWithClass(1);
+
+        var r = await svc.GrantAsync(v, 1, isWin: true, BattleXpMode.Rank);
+
+        Assert.That(r.Level, Is.EqualTo(2));
+        Assert.That(r.LeveledUp, Is.True);
+    }
+
+    [Test]
+    public async Task LeveledUp_stays_true_across_multiple_bumps_in_one_grant()
+    {
+        // Grant crosses L1→L2→L3 in one go.
+        var svc = NewService(new BattleXpConfig { XpPerWin = 500 });
+        var v = NewViewerWithClass(1);
+
+        var r = await svc.GrantAsync(v, 1, isWin: true, BattleXpMode.Rank);
+
+        Assert.That(r.Level, Is.EqualTo(3));
+        Assert.That(r.LeveledUp, Is.True);
+    }
 }