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>

app.py

@@ -20,7 +20,7 @@ from . import APP_NAME, DISPLAY_NAME, __version__
 from .config import PROVIDER_LABELS, AppConfig
 from .i18n import LANGUAGE_SHORT, LANGUAGES, get_language, on_language_changed, set_language, tr
 from .state import AppContext
-from .ui.widgets import widen_popup
+from .ui.widgets import tidy_popup
 from .theme import current_palette, set_active_theme, stylesheet
 from .core.task_scheduler import TaskScheduler
 from .ui.cowork_tab import CoworkTab
@@ -261,7 +261,7 @@ class MainWindow(QMainWindow):
         self.nav_project.setObjectName("navProjectPick")
         self.nav_project.setToolTip(tr("app.nav.project_pick"))
         self.nav_project.currentIndexChanged.connect(self._on_rail_project_pick)
-        widen_popup(self.nav_project)
+        tidy_popup(self.nav_project)
         self.nav_new_chat = QPushButton(tr("cowork.new_chat"))
         self.nav_new_chat.setObjectName("navNewChatBtn")
         self.nav_new_chat.setIcon(_icon("plus"))
@@ -675,7 +675,7 @@ class MainWindow(QMainWindow):
             if idx >= 0:
                 self.nav_project.setCurrentIndex(idx)
             has = bool(choices)
-            widen_popup(self.nav_project)
+            tidy_popup(self.nav_project)
             self.nav_project.setEnabled(has)
             self.nav_project_btn.setEnabled(has)
             self.nav_project_btn.setToolTip(
@@ -991,7 +991,7 @@ class MainWindow(QMainWindow):
         idx = self.language_combo.findData(get_language())
         if idx >= 0:
             self.language_combo.setCurrentIndex(idx)
-        widen_popup(self.language_combo)
+        tidy_popup(self.language_combo)
         self.language_combo.currentIndexChanged.connect(self._on_language_changed)
         who.addWidget(self.language_combo)
         self.theme_btn = self._build_theme_button()
@@ -1005,7 +1005,7 @@ class MainWindow(QMainWindow):
         self.provider_combo.setToolTip(tr("app.provider"))
         for key, label in PROVIDER_LABELS.items():
             self.provider_combo.addItem(label, key)
-        widen_popup(self.provider_combo)
+        tidy_popup(self.provider_combo)
         idx = self.provider_combo.findData(self.ctx.config.active_provider)
         if idx >= 0:
             self.provider_combo.setCurrentIndex(idx)