Add deck synergy suggestions, a responsive deck layout, and undoable library bulk-add

Suggestion scoring is fully offline (tribal/mechanic/archetype/mana-base
signals derived at ingest, no external synergy database), with an "unusual
picks" mode that surfaces underappreciated cards instead of staples. The
deck page's top panels now use a CSS grid so wide windows don't waste
horizontal space. Library's bulk add-to-deck can clobber existing deck
quantities, so it now offers an undo (snackbar + command palette, the
latter with no timeout) that restores each card's prior state exactly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/components.tsx

@@ -279,6 +279,31 @@ export function InfoDialog({
   );
 }
 
+/** Floating snackbar offering to reverse the caller's last action. Auto-
+ * dismisses on a timer managed by the caller (this component is purely
+ * presentational) — pass `null`/omit rendering it once the window lapses. */
+export function UndoBar({
+  message,
+  onUndo,
+  onDismiss,
+}: {
+  message: string;
+  onUndo: () => void;
+  onDismiss: () => void;
+}) {
+  return (
+    <div className="undo-bar">
+      <span>{message}</span>
+      <button className="primary" onClick={onUndo}>
+        Undo
+      </button>
+      <button className="undo-bar-close" onClick={onDismiss} title="Dismiss">
+        ×
+      </button>
+    </div>
+  );
+}
+
 /** Modal shuffle-and-draw sample hand: shows the drawn cards and lets the
  * caller draw more or reshuffle, on top of a click/Escape-to-close backdrop. */
 export function SampleHandModal({