refactor: rename Scan deck tab -> Audio (deck wiring only)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_ui_structure.py

@@ -55,7 +55,7 @@ def test_workers_spinbox_in_export_tab(win):
 
 def test_scan_button_in_scan_tab(win):
     from PyQt6.QtWidgets import QPushButton
-    assert win._btn_scan in win._tab_scan.findChildren(QPushButton)
+    assert win._btn_scan in win._tab_audio.findChildren(QPushButton)
 
 
 def test_portrait_combo_in_crop_tab(win):
@@ -106,7 +106,7 @@ def test_side_by_side_menu_pins_third_panel(win):
     # (there's no tab bar to right-click). Suppress the QSettings save via the
     # _deck_loading guard so this doesn't leak into other windows.
     win._tab_export._pinned = True
-    win._tab_scan._pinned = True
+    win._tab_audio._pinned = True
     win._refresh_deck_layout()
     assert len(_split_columns(win)) == 2
     act = next(a for a, p in win._deck_pin_actions if p is win._tab_crop)
@@ -271,3 +271,14 @@ def test_audio_region_tracks_cursor_and_length(win):
     win._file_path = ""
     win._update_audio_region()
     assert win._timeline._audio_region is None
+
+
+def test_audio_deck_tab_exists(win):
+    # The old "Scan" deck tab is now "Audio".
+    assert hasattr(win, "_tab_audio")
+    assert win._tab_audio._deck_key == "audio"
+    assert win._tab_audio in win._deck_panels
+    assert not hasattr(win, "_tab_scan")
+    labels = [win._control_deck.tabText(i)
+              for i in range(win._control_deck.count())]
+    assert "Audio" in labels and "Scan" not in labels