Restore Apply UV2 for source-only repacks

Documentation~/EXPERIMENTS.md

@@ -351,3 +351,11 @@
 - EditMode red/green: `TransferTargetDetection_IgnoresSourceOnlySelection`.
 - EditMode red/green: `Uv2PixelMargin_ScalesFromResolvedAtlasSize`.
 - Full model benchmark (Carousel/Playground/WateringCan) в этом checkout не прогнан: тестовые FBX/`BenchmarkReports/` отсутствуют в репозитории. Нужен ручной Unity прогон на suite для финального сравнения `repackMs`, `density spread`, `overlapShellPairs`, `invertedCount`, `texelDensityBadCount`.
+
+## Эксперимент 2026-08-06 — Apply UV2 после source-only repack
+
+**Проблема:** оптимизация source-only pipeline корректно пропускала transfer, но оставляла `HasTransfer = false`. Из-за общего UI-gate результат repack нельзя было применить к FBX.
+
+**Изменение:** Quality Report и Validation Overlay по-прежнему требуют завершённого transfer, а Apply/Reset actions теперь доступны после repack или transfer. Transfer и auto-tune для source-only workflow остаются пропущенными.
+
+**Проверка:** EditMode-тест `ApplyUv2_IsAvailable_AfterSourceOnlyRepack` фиксирует доступность Apply при `HasRepack = true` и `HasTransfer = false`.

Editor/Tools/LightmapTransferTool.cs

@@ -44,6 +44,11 @@ static bool HasIncludedTransferTargets(IEnumerable<MeshEntry> entries, int sourc
             return false;
         }
 
+        static bool CanApplyUv2(bool hasRepack, bool hasTransfer)
+        {
+            return hasRepack || hasTransfer;
+        }
+
         // ── Internal tab ──
         enum Tab { Setup, Repack, Transfer }
         Tab tab = Tab.Setup;
@@ -1259,19 +1264,13 @@ void DrawTransfer()
                         EditorStyles.miniLabel);
                     EditorGUI.indentLevel--;
                 }
+            }
 
+            if (CanApplyUv2(ctx.HasRepack, ctx.HasTransfer))
+            {
                 EditorGUILayout.Space(6);
-                // Post-transfer actions — what you do immediately after a
-                // successful UV2 transfer (apply to FBX / reset).
-                //
-                // FBX export ("Overwrite FBX" / "Export New FBX" /
-                // "Backup from main") and "Save Mesh Assets" live in the
-                // sidebar footer for any tab; duplicating them here was
-                // confusing redundancy.
-                //
-                // "Generate LODs" was rendered here too, but LOD generation
-                // is the job of the dedicated LOD Gen tab — keeping it on
-                // Transfer made the tab feel scope-creepy.
+                // The source LOD can be applied immediately after repack,
+                // even when there are no included target LODs to transfer.
                 H("Apply UV2");
                 ColorBtn(new Color(.3f,.85f,.4f), "Apply UV2 to FBX", 26, ApplyUv2ToFbx);
                 EditorGUILayout.Space(2);

Tests/Editor/XatlasRepackGroupMergeTests.cs

@@ -224,5 +224,19 @@ public void TransferTargetDetection_IgnoresSourceOnlySelection()
                     Object.DestroyImmediate(e.originalMesh);
             }
         }
+
+        [Test]
+        public void ApplyUv2_IsAvailable_AfterSourceOnlyRepack()
+        {
+            var method = typeof(LightmapTransferTool).GetMethod(
+                "CanApplyUv2",
+                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
+            Assert.IsNotNull(method, "LightmapTransferTool should expose the Apply UV2 availability rule as a testable helper");
+
+            Assert.IsTrue((bool)method.Invoke(null, new object[] { true, false }),
+                "A source-only repack must remain applyable when transfer is skipped.");
+            Assert.IsTrue((bool)method.Invoke(null, new object[] { false, true }));
+            Assert.IsFalse((bool)method.Invoke(null, new object[] { false, false }));
+        }
     }
 }