feat(application): DeactivateRubroCommandHandler guard contra Products activos

Extiende IProductQueryRepository con CountActiveByRubroAsync, inyecta
el repositorio en el handler e intercala el chequeo después del guard
de hijos activos. Tests de unidad cubren: throw, success con 0 productos,
y estabilidad del orden de guardas (hijos primero).

src/api/SIGCM2.Application/Abstractions/Persistence/IProductQueryRepository.cs

@@ -12,4 +12,10 @@ public interface IProductQueryRepository
     /// Used by DeactivateProductTypeCommandHandler to guard against orphaning active products.
     /// </summary>
     Task<bool> ExistsActiveByProductTypeAsync(int productTypeId, CancellationToken ct = default);
+
+    /// <summary>
+    /// Returns the count of active Products where RubroId = rubroId.
+    /// Used by DeactivateRubroCommandHandler to guard against orphaning active products. (issue #41)
+    /// </summary>
+    Task<int> CountActiveByRubroAsync(int rubroId, CancellationToken ct = default);
 }

src/api/SIGCM2.Application/Rubros/Deactivate/DeactivateRubroCommandHandler.cs

@@ -10,15 +10,18 @@ public sealed class DeactivateRubroCommandHandler : ICommandHandler<DeactivateRu
 {
     private readonly IRubroRepository _repo;
     private readonly IAuditLogger _audit;
+    private readonly IProductQueryRepository _productQuery;
     private readonly TimeProvider _timeProvider;
 
     public DeactivateRubroCommandHandler(
         IRubroRepository repo,
         IAuditLogger audit,
+        IProductQueryRepository productQuery,
         TimeProvider timeProvider)
     {
         _repo = repo;
         _audit = audit;
+        _productQuery = productQuery;
         _timeProvider = timeProvider;
     }
 
@@ -31,6 +34,10 @@ public sealed class DeactivateRubroCommandHandler : ICommandHandler<DeactivateRu
         if (activeChildren > 0)
             throw new RubroTieneHijosActivosException(command.Id, activeChildren);
 
+        var productosActivos = await _productQuery.CountActiveByRubroAsync(command.Id);
+        if (productosActivos > 0)
+            throw new RubroConProductosActivosException(command.Id, productosActivos);
+
         var deactivated = target.WithActivo(false, _timeProvider);
 
         using var tx = new TransactionScope(

tests/SIGCM2.Application.Tests/Rubros/Deactivate/DeactivateRubroCommandHandlerTests.cs

@@ -13,6 +13,7 @@ public class DeactivateRubroCommandHandlerTests
 {
     private readonly IRubroRepository _repo = Substitute.For<IRubroRepository>();
     private readonly IAuditLogger _audit = Substitute.For<IAuditLogger>();
+    private readonly IProductQueryRepository _productQuery = Substitute.For<IProductQueryRepository>();
     private readonly FakeTimeProvider _timeProvider = new(new DateTimeOffset(2026, 4, 18, 12, 0, 0, TimeSpan.Zero));
     private readonly DeactivateRubroCommandHandler _handler;
 
@@ -22,7 +23,8 @@ public class DeactivateRubroCommandHandlerTests
     public DeactivateRubroCommandHandlerTests()
     {
         _repo.CountActiveChildrenAsync(Arg.Any<int>(), Arg.Any<CancellationToken>()).Returns(0);
-        _handler = new DeactivateRubroCommandHandler(_repo, _audit, _timeProvider);
+        _productQuery.CountActiveByRubroAsync(Arg.Any<int>(), Arg.Any<CancellationToken>()).Returns(0);
+        _handler = new DeactivateRubroCommandHandler(_repo, _audit, _productQuery, _timeProvider);
     }
 
     // ── Happy path: leaf soft-delete ─────────────────────────────────────────
@@ -103,4 +105,43 @@ public class DeactivateRubroCommandHandlerTests
 
         await act.Should().ThrowAsync<RubroNotFoundException>();
     }
+
+    // ── Active Products guard (issue #41) ────────────────────────────────────
+
+    [Fact]
+    public async Task Deactivate_WithActiveProducts_ThrowsRubroConProductosActivosException()
+    {
+        _repo.GetByIdAsync(10, Arg.Any<CancellationToken>()).Returns(LeafRubro(10));
+        _productQuery.CountActiveByRubroAsync(10, Arg.Any<CancellationToken>()).Returns(3);
+
+        var act = () => _handler.Handle(new DeactivateRubroCommand(Id: 10));
+
+        await act.Should().ThrowAsync<RubroConProductosActivosException>()
+            .Where(ex => ex.RubroId == 10 && ex.ProductosActivosCount == 3);
+    }
+
+    [Fact]
+    public async Task Deactivate_WithZeroActiveProducts_Succeeds()
+    {
+        _repo.GetByIdAsync(10, Arg.Any<CancellationToken>()).Returns(LeafRubro(10));
+        _productQuery.CountActiveByRubroAsync(10, Arg.Any<CancellationToken>()).Returns(0);
+
+        var result = await _handler.Handle(new DeactivateRubroCommand(Id: 10));
+
+        result.Activo.Should().BeFalse();
+    }
+
+    [Fact]
+    public async Task Deactivate_WithActiveChildrenAndProducts_ThrowsChildrenFirst()
+    {
+        // Children guard fires BEFORE products guard — order of checks must be stable.
+        _repo.GetByIdAsync(5, Arg.Any<CancellationToken>()).Returns(LeafRubro(5));
+        _repo.CountActiveChildrenAsync(5, Arg.Any<CancellationToken>()).Returns(2);
+        _productQuery.CountActiveByRubroAsync(5, Arg.Any<CancellationToken>()).Returns(3);
+
+        var act = () => _handler.Handle(new DeactivateRubroCommand(Id: 5));
+
+        // Children exception must win — products guard is never reached
+        await act.Should().ThrowAsync<RubroTieneHijosActivosException>();
+    }
 }