Revert "fix: Resolve canvas reference and duplicate currentTool declaration"

This reverts commit a948fab619.

js/main.js

@@ -1,6 +1,6 @@
 // Main game variables and initialization
 let canvas, ctx;
-// currentTool is already defined in input.js
+let currentTool = SAND;
 let lastFrameTime = 0;
 let fps = 0;
 let debugMode = false;