chore: use command -v instead of which

The `which` command is not always available whereas `command -v`
is a POSIX built-in.

Author: calebdw

src/Install/CodeEnvironment/ClaudeCode.php

@@ -25,7 +25,7 @@ public function systemDetectionConfig(Platform $platform): array
     {
         return match ($platform) {
             Platform::Darwin, Platform::Linux => [
-                'command' => 'which claude',
+                'command' => 'command -v claude',
             ],
             Platform::Windows => [
                 'command' => 'where claude 2>null',

src/Install/CodeEnvironment/VSCode.php

@@ -26,7 +26,7 @@ public function systemDetectionConfig(Platform $platform): array
                 'paths' => ['/Applications/Visual Studio Code.app'],
             ],
             Platform::Linux => [
-                'command' => 'which code',
+                'command' => 'command -v code',
             ],
             Platform::Windows => [
                 'paths' => [