Merge views into Match, expand history, and polish the UI

- Match page now holds players/match info, turn stats with a turn
  picker, and the deck lists (My deck · Preview · Opponent); the Deck
  and Turn tabs are gone. Section heights are draggable and remembered.
- History: sortable, resizable columns; deck and commander columns;
  right-click to show only or hide games with a value, with filter
  chips; stats tiles (win rate overall, last 10/100, last 7 days,
  play/draw, average length and turns) that follow the filters.
  Commanders are backfilled for games recorded before they were stored.
- Deck panel shows copies per zone against the deck total (e.g. 2/5).
- Preview can be cleared with ✕, a click on the image, or Esc.
- Customize menu stays open while toggling; Arrange covers deck
  sections and turn stats together.
- Fix squeezed nav buttons and the header pushing controls off-screen.
- Fix known opponent cards being double-counted when also revealed.

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

src/mtga_assistant/ui/preview.py

@@ -2,15 +2,17 @@
 
 from __future__ import annotations
 
-from PySide6.QtCore import QSize, Qt
-from PySide6.QtGui import QPixmap, QResizeEvent
-from PySide6.QtWidgets import QLabel, QSizePolicy, QVBoxLayout, QWidget
+from PySide6.QtCore import QSize, Qt, Signal
+from PySide6.QtGui import QMouseEvent, QPixmap, QResizeEvent
+from PySide6.QtWidgets import QHBoxLayout, QLabel, QSizePolicy, QToolButton, QVBoxLayout, QWidget
 
 from ..carddb import CardDB
 from ..images import ImageCache
 
 
 class CardPreview(QWidget):
+    cleared = Signal()
+
     def __init__(self, cards: CardDB, images: ImageCache, parent=None):
         super().__init__(parent)
         self.cards = cards
@@ -26,18 +28,44 @@ class CardPreview(QWidget):
         self.caption.setWordWrap(True)
         self.caption.setAlignment(Qt.AlignmentFlag.AlignCenter)
 
+        self.close_btn = QToolButton()
+        self.close_btn.setText("✕")
+        self.close_btn.setToolTip("Stop previewing this card (Esc, or click the image)")
+        self.close_btn.clicked.connect(self.clear)
+        top = QHBoxLayout()
+        top.addStretch(1)
+        top.addWidget(self.close_btn)
+
         lay = QVBoxLayout(self)
         lay.setContentsMargins(4, 4, 4, 4)
+        lay.addLayout(top)
         lay.addWidget(self.image, 1)
         lay.addWidget(self.caption)
 
         images.image_ready.connect(self._on_image_ready)
+        self.clear()
+
+    def clear(self) -> None:
+        """Back to the empty state."""
+        was_showing = self.grp_id is not None
+        self.grp_id = None
+        self.caption.setText("")
         self._show_placeholder("Hover a card to preview it")
+        self.close_btn.setVisible(False)
+        if was_showing:
+            self.cleared.emit()
+
+    def mousePressEvent(self, event: QMouseEvent) -> None:
+        if event.button() == Qt.MouseButton.LeftButton and self.grp_id is not None:
+            self.clear()
+            return
+        super().mousePressEvent(event)
 
     def show_card(self, grp_id: int) -> None:
         if grp_id == self.grp_id:
             return
         self.grp_id = grp_id
+        self.close_btn.setVisible(True)
         info = self.cards.get(grp_id)
         details = [info.type_line]
         if info.power or info.toughness: