Fix elimination check to only eliminate when piece blocks are above visible area

Previously, players were eliminated when currentPiece.y <= 0, which was too
aggressive. Pieces like I, T, S, Z, J, L spawn at y=0 but have empty top rows,
so their actual blocks are at y >= 1 and visible on the board.

Now we check if any part of the locked piece is actually above y=0 (not
visible) before eliminating the player.

public/js/game.js

@@ -226,7 +226,21 @@ class TetrisGame {
     }
 
     // Check for game over (piece locked above visible area)
-    if (this.currentPiece.y <= 0) {
+    // Only eliminate if any part of the piece is above y=0 (not visible)
+    let pieceAboveBoard = false;
+    for (let row = 0; row < this.currentPiece.shape.length; row++) {
+      for (let col = 0; col < this.currentPiece.shape[row].length; col++) {
+        if (this.currentPiece.shape[row][col]) {
+          const boardY = this.currentPiece.y + row;
+          if (boardY < 0) {
+            pieceAboveBoard = true;
+            break;
+          }
+        }
+      }
+      if (pieceAboveBoard) break;
+    }
+    if (pieceAboveBoard) {
       this.gameOver = true;
       this.eliminated = true;
     }