Add section toggles, simplify Customize, scope header to Match

- Customize menu: a "Sections" group to show/hide each Match panel
  (You, Match, Opponent, Turn stats, My deck, Preview, Opponent's
  cards); rows collapse when all their panels are hidden. Player panel
  details follow, then Arrange. The submenus duplicating Arrange are gone.
- The top bar's match summary only shows on the Match tab.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/mtga_assistant/ui/match_view.py

@@ -214,7 +214,8 @@ class MatchView(QWidget):
             grid.addWidget(w, row, 0, Qt.AlignmentFlag.AlignHCenter)
         grid.setRowStretch(7, 1)
 
-        top = QWidget()
+        self.turn_view = turn_view
+        top = self.top = QWidget()
         top_lay = QHBoxLayout(top)
         top_lay.setContentsMargins(0, 0, 0, 0)
         top_lay.addWidget(self.me, 3)
@@ -233,11 +234,26 @@ class MatchView(QWidget):
         lay = QVBoxLayout(self)
         lay.setContentsMargins(0, 0, 0, 0)
         lay.addWidget(self.split)
+        self._panels = {"you": True, "match": True, "opponent": True}
+        self._has_game = False
+
+    def show_panels(self, you: bool, match: bool, opponent: bool, turns: bool) -> None:
+        """Hide/show panels; a row with every panel hidden collapses out of the splitter."""
+        self._panels = {"you": you, "match": match, "opponent": opponent}
+        self.top.setVisible(you or match or opponent)
+        self.turn_view.setVisible(turns)
+        self._apply_panels()
+
+    def _apply_panels(self) -> None:
+        # render() toggles these for "no game yet", so combine both conditions.
+        self.me.setVisible(self._has_game and self._panels["you"])
+        self.info.setVisible(self._has_game and self._panels["match"])
+        self.opp.setVisible(self._has_game and self._panels["opponent"])
 
     def render(self, t: MatchTracker, now_ms: int) -> None:
         g = t.game
-        for w in (self.me, self.opp, self.info):
-            w.setVisible(g is not None)
+        self._has_game = g is not None
+        self._apply_panels()
         if g is None:
             return
         self.me.render(g, g.my_seat, "You", now_ms)