Drop the tick from drop-lists; the row is already tinted

The selected row carries selection-background-color, so a checkmark repeats
what the colour says — and in a combo as wide as "VN" it repeated it on top of
the letters. A combo's default delegate paints menu-style, which is where the
glyph comes from; a plain QStyledItemDelegate paints item-view style, which has
none. widen_popup does both jobs now, so it is tidy_popup.

check_combo_popup additionally requires the delegate to be the plain one and the
stylesheet to still tint the current row — removing the delegate line fails it.

21/21 checkers pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tools/check_combo_popup.py

@@ -50,6 +50,7 @@ def main() -> int:
     app.processEvents()
 
     fails = []
+    from PySide6.QtWidgets import QStyledItemDelegate
     for name in ("language_combo", "nav_project", "provider_combo"):
         combo = getattr(win, name, None)
         if combo is None or not combo.count():
@@ -66,6 +67,20 @@ def main() -> int:
         if have < need:
             fails.append(f"{name}: popup {have}px, khong du {need}px cho chu + dau tick")
 
+        # No tick: the row is already tinted, and the menu-style delegate that
+        # draws one on macOS covered the two letters it was marking.
+        deleg = combo.itemDelegate()
+        plain = type(deleg) is QStyledItemDelegate
+        print(f"{'':15}  delegate={type(deleg).__name__} (khong ve dau tick={plain})")
+        if not plain:
+            fails.append(f"{name}: dung delegate kieu menu — macOS se ve dau tick")
+
+        # ...and the current row must still be obvious without one.
+        view = combo.view()
+        sheet = app.styleSheet()
+        if "selection-background-color" not in sheet:
+            fails.append("popup khong to mau muc dang chon")
+
     print()
     for f in fails:
         print("FAIL  " + f)