fix(dialog): improve escape key handling for dialogs

The handling of the Escape key has been refined to ensure that it
closes the correct dialog based on the current state. Additionally,
the z-index for the compare dialog backdrop has been updated to
ensure proper layering with other dialogs.

- Enhanced Escape key functionality for better user experience
- Updated z-index for compare dialog backdrop to avoid overlap

src/App.svelte

@@ -3967,10 +3967,10 @@
       helpOpen = false;
       return;
     }
-    if (event.key === "Escape" && fileHistoryDialogOpen && !isBusy) closeFileHistoryDialog();
+    if (event.key === "Escape" && compareDialogOpen) closeCompareDialog();
+    else if (event.key === "Escape" && fileHistoryDialogOpen && !isBusy) closeFileHistoryDialog();
     else if (event.key === "Escape" && repoTabContextMenu) closeRepoTabContextMenu();
     else if (event.key === "Escape" && pendingDiscard && !isBusy) closeDiscardConfirm();
-    else if (event.key === "Escape" && compareDialogOpen) closeCompareDialog();
     else if (event.key === "Escape" && newBranchCommit) newBranchCommit = null;
     else if (event.key === "Escape" && renameBranchTarget) renameBranchTarget = null;
     else if (event.key === "Escape" && deleteBranchTarget) closeDeleteBranchDialog();