debug(input): log drag failures to browser console for diagnosis

Add warn!/info! calls to start_drag so every click that doesn't produce
a drag emits a console line with the cursor world position, stock/waste
sizes, and per-tableau pile lengths. This lets us see in browser DevTools
whether find_draggable_at is returning None (wrong hit position) or
something earlier in the pipeline is blocking.

Remove once root cause is identified.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/input_plugin.rs

@@ -621,15 +621,35 @@ fn start_drag(
     {
         return;
     }
-    let Some(layout) = layout else { return };
+    let Some(layout) = layout else {
+        bevy::log::warn!("[drag] no layout — skipping");
+        return;
+    };
     let Some(world) = cursor_world(&windows, &cameras) else {
+        bevy::log::warn!("[drag] cursor_world returned None (no camera?)");
         return;
     };
 
     // Don't pick up the stock — that is handled by handle_stock_click.
     let Some((pile, stack_index, card_ids)) = find_draggable_at(world, &game.0, &layout.0) else {
+        bevy::log::info!(
+            "[drag] no draggable at world {:?} — stock={:?} waste_len={} tab_lens={:?}",
+            world,
+            layout.0.pile_positions.get(&KlondikePile::Stock),
+            game.0.waste_cards().len(),
+            [
+                game.0.pile(KlondikePile::Tableau(Tableau::Tableau1)).len(),
+                game.0.pile(KlondikePile::Tableau(Tableau::Tableau2)).len(),
+                game.0.pile(KlondikePile::Tableau(Tableau::Tableau3)).len(),
+                game.0.pile(KlondikePile::Tableau(Tableau::Tableau4)).len(),
+                game.0.pile(KlondikePile::Tableau(Tableau::Tableau5)).len(),
+                game.0.pile(KlondikePile::Tableau(Tableau::Tableau6)).len(),
+                game.0.pile(KlondikePile::Tableau(Tableau::Tableau7)).len(),
+            ]
+        );
         return;
     };
+    bevy::log::info!("[drag] started: pile={:?} stack_index={} cards={:?}", pile, stack_index, card_ids);
 
     let bottom_pos = card_position(&game.0, &layout.0, &pile, stack_index);