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>

README.md

@@ -25,9 +25,10 @@ Two views, switched from the top bar (Ctrl+1 / Ctrl+2):
   filters. Click a game to open it in the Match view ("Back to live" returns). Games from the
   previous MTGA session (`Player-prev.log`) are imported on startup.
 
-*⚙ Customize* shows or hides the match panels, turn stats, deck sections and the preview.
-*Customize → Arrange…* reorders (drag, or ↑/↓) and shows/hides the My deck and Opponent sections
-and the turn stats. Your choices are remembered.
+*⚙ Customize* shows or hides each panel of the Match page (You, Match, Opponent, Turn stats,
+My deck, Preview, Opponent's cards) and the details in the player panels. *Customize → Arrange…*
+reorders (drag, or ↑/↓) and shows/hides the My deck and Opponent sections and the turn stats.
+Your choices are remembered.
 
 Card names, mana costs and types come from MTGA's own local card database, so they work offline.