Column Win Check Missing

Title:
Win Check for Columns Missing

Description:
In the current implementation, the game checks for row and diagonal wins, but column wins are not checked. This causes the game to miss a victory when all spots in a column are filled by the same player.

Expected Behavior:
The game should declare a win when a player fills all spots in any column.

Suggested Fix:
Add logic in the checkWin() function to check columns for the winning condition.

Find the `checkWin()` function in the codebase, likely in a game logic file. Examine the existing row and diagonal checks. Add a loop to iterate through columns, checking if all cells in a column belong to the same player. Test by playing a game where a column is filled to verify the win is detected.

索引モデルが issue の本文から書いたものです。