Improve error handling in Counter deployment script

script/Counter.s.sol

@@ -2,11 +2,38 @@
 pragma solidity ^0.8.13;
 
 import {Script, console} from "forge-std/Script.sol";
+import {Counter} from "../src/Counter.sol";
 
+/// @title Counter Deployment Script
+/// @notice This script deploys a new Counter contract to the network
 contract CounterScript is Script {
+    /// @notice Custom error for missing private key
+    error MissingPrivateKey();
+
+    /// @notice Setup function that runs before the main deployment
     function setUp() public {}
 
+    /// @notice Main deployment function
+    /// @dev Requires PRIVATE_KEY environment variable to be set
     function run() public {
-        vm.broadcast();
+        // Get deployer private key from environment
+        uint256 deployerPrivateKey;
+        try vm.envUint("PRIVATE_KEY") returns (uint256 key) {
+            deployerPrivateKey = key;
+        } catch {
+            console.error("Error: PRIVATE_KEY environment variable not set");
+            console.error("Please set your private key using: export PRIVATE_KEY=your_private_key");
+            revert MissingPrivateKey();
+        }
+
+        // Start broadcasting transactions
+        vm.startBroadcast(deployerPrivateKey);
+
+        // Deploy the Counter contract
+        Counter counter = new Counter();
+        console.log("Counter deployed at:", address(counter));
+
+        // Stop broadcasting transactions
+        vm.stopBroadcast();
     }
 }