feat: redesign Batch tab with two-column layout matching Single tab

Restructure the Batch tab from a vertical stack to a side-by-side
layout (file upload left, file download right) with a full-width
preview table below, matching the Single tab's structure for visual
consistency when switching tabs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app.py

@@ -229,13 +229,16 @@ def _build_demo() -> gr.Blocks:
                     )
 
                 with gr.Tab("Batch"):
-                    gr.Markdown("Upload a `.txt` file (one sentence per line) or a `.csv` file with a `text` column.")
-                    batch_input = gr.File(label="Upload file", file_types=[".txt", ".csv"])
+                    with gr.Row():
+                        batch_input = gr.File(
+                            label="Upload file (.txt, one sentence per line, or .csv with 'text' column)",
+                            file_types=[".txt", ".csv"],
+                        )
+                        batch_output = gr.File(label="Download translations", interactive=False)
 
                     batch_btn = gr.Button("Translate", variant="primary")
 
                     batch_preview = gr.Dataframe(label="Preview", interactive=False)
-                    batch_output = gr.File(label="Download translations", interactive=False)
 
                     batch_btn.click(
                         fn=translate_batch,

tests/test_app.py

@@ -329,6 +329,13 @@ def test_dataframe_is_non_interactive(demo):
     assert dataframes[0].interactive is False
 
 
+def test_batch_tab_has_row_layout(demo):
+    """Batch tab should use a Row for side-by-side upload/download layout."""
+    # Rows: outer layout + Single tab + Batch tab = 3
+    rows = [b for b in demo.blocks.values() if type(b).__name__ == "Row"]
+    assert len(rows) == 3, f"Expected 3 Rows (outer + Single + Batch), found {len(rows)}"
+
+
 # --- UI component tests ---
 
 
@@ -404,11 +411,13 @@ def test_dropdown_default_is_french(demo):
 
 
 def test_file_upload_accepts_txt_and_csv(demo):
-    """File upload component should accept .txt and .csv files."""
+    """File upload component should accept .txt and .csv files with instructions in label."""
     file_components = [b for b in demo.blocks.values() if type(b).__name__ == "File"]
     upload_files = [f for f in file_components if f.file_types is not None]
     assert len(upload_files) >= 1
     assert set(upload_files[0].file_types) == {".txt", ".csv"}
+    assert ".txt" in upload_files[0].label
+    assert ".csv" in upload_files[0].label
 
 
 def test_batch_output_is_non_interactive(demo):