feat: asset deletion scan and delete dialog (WIP)

Adds AssetDeletionScan to Core (no UI/editor-pipeline deps, invariant holds)
and SAssetDeleteDialog to the Editor module, plus 10 spec cases.

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

Source/AssetUsageAuditEditor/Private/SAssetUsageAuditPanel.cpp

@@ -12,6 +12,7 @@
 #include "AssetUsageExporter.h"
 #include "AssetUsagePaths.h"
 #include "AssetUsageReportWriter.h"
+#include "SAssetDeleteDialog.h"
 #include "AssetRegistry/AssetRegistryModule.h"
 #include "AssetRegistry/IAssetRegistry.h"
 #include "Algo/AllOf.h"
@@ -580,6 +581,33 @@ void SAssetUsageAuditPanel::Construct(const FArguments& InArgs)
                 .OnClicked(this, &SAssetUsageAuditPanel::OnExportFilesClicked)
                 .IsEnabled(this, &SAssetUsageAuditPanel::HasCheckedAssets)
             ]
+
+            // Delete sits last and behind a separator, deliberately. It acts on the same ticked
+            // set as Export, so it belongs on this bar, but it is the only irreversible action in
+            // the tool and must never be the button someone reaches by muscle memory.
+            + SHorizontalBox::Slot()
+            .AutoWidth()
+            .VAlign(VAlign_Center)
+            .Padding(8.0f, 2.0f, 2.0f, 2.0f)
+            [
+                SNew(SSeparator)
+                .Orientation(Orient_Vertical)
+            ]
+
+            + SHorizontalBox::Slot()
+            .AutoWidth()
+            .VAlign(VAlign_Center)
+            .Padding(2.0f, 0.0f)
+            [
+                SNew(SButton)
+                .Text(LOCTEXT("DeleteTicked", "Delete ticked assets..."))
+                .ToolTipText(LOCTEXT("DeleteTickedTip",
+                    "Permanently delete the ticked assets from the project. Levels are never deleted. "
+                    "Shows what still references them before anything is removed."))
+                .ButtonColorAndOpacity(FLinearColor(0.55f, 0.16f, 0.16f))
+                .OnClicked(this, &SAssetUsageAuditPanel::OnDeleteClicked)
+                .IsEnabled(this, &SAssetUsageAuditPanel::HasCheckedAssets)
+            ]
         ]
     ];
 }
@@ -2224,6 +2252,83 @@ FReply SAssetUsageAuditPanel::OnExportFilesClicked()
     return FReply::Handled();
 }
 
+// --- Deleting ----------------------------------------------------------------------------------
+
+FReply SAssetUsageAuditPanel::OnDeleteClicked()
+{
+    TArray<FAssetUsageRow> Rows;
+    GetCheckedRows(Rows);
+
+    if (Rows.IsEmpty())
+    {
+        return FReply::Handled();
+    }
+
+    TArray<FName> Packages;
+    Packages.Reserve(Rows.Num());
+
+    for (const FAssetUsageRow& Row : Rows)
+    {
+        Packages.Add(Row.PackageName);
+    }
+
+    // Deliberately NOT widened with the dependency closure, unlike export. Export widens so that a
+    // mesh arrives with its materials; widening a delete the same way would destroy content nobody
+    // ticked, and a single shared texture would drag half the project along with it. Delete acts on
+    // exactly what was ticked, and never on more.
+    const FAssetDeleteOutcome Outcome = ShowAssetDeleteDialog(Packages);
+
+    if (Outcome.bCancelled)
+    {
+        StatusText = LOCTEXT("DeleteCancelled", "Delete cancelled - nothing was changed.");
+        return FReply::Handled();
+    }
+
+    ForgetDeletedPackages(Outcome.DeletedPackages);
+
+    StatusText = FText::Format(
+        LOCTEXT("DeleteFinished",
+            "Deleted {0} of {1} ticked asset(s); {2} were refused. Reference counts elsewhere in this result are now out of date - run the audit again."),
+        FText::AsNumber(Outcome.DeletedPackages.Num()),
+        FText::AsNumber(Outcome.Requested),
+        FText::AsNumber(Outcome.Refused));
+
+    return FReply::Handled();
+}
+
+void SAssetUsageAuditPanel::ForgetDeletedPackages(const TArray<FName>& DeletedPackages)
+{
+    if (DeletedPackages.IsEmpty())
+    {
+        return;
+    }
+
+    const TSet<FName> Gone(DeletedPackages);
+
+    LastResult.Rows.RemoveAll([&Gone](const FAssetUsageRow& Row)
+    {
+        return Gone.Contains(Row.PackageName);
+    });
+
+    AllRows.RemoveAll([&Gone](const FAssetUsageRowPtr& Row)
+    {
+        return Row.IsValid() && Gone.Contains(Row->PackageName);
+    });
+
+    for (FName Package : DeletedPackages)
+    {
+        CheckedPackages.Remove(Package);
+    }
+
+    // Removing the rows is honest but incomplete: everything that referenced them still carries the
+    // reference counts it had before, and an asset that was UsedByAssetsOnly through a now-deleted
+    // Blueprint has a different verdict than the one on screen. Marking the result stale says so,
+    // rather than leaving figures that look freshly measured.
+    bResultStale = true;
+
+    RebuildFilteredRows();
+}
+
 void SAssetUsageAuditPanel::RunMigrateExport(const TArray<FAssetUsageRow>& Rows, const FAssetExportRequest& Request)
 {
     TArray<FName> Packages;