fix: use cross-platform az CLI detection (az version instead of which)

extensions/microsoft-foundry/index.ts

@@ -22,7 +22,8 @@ function execCmd(cmd: string): string {
 
 function isAzCliInstalled(): boolean {
   try {
-    execCmd("which az");
+    // "az version" works on Windows, Linux, and macOS
+    execCmd("az version --output none");
     return true;
   } catch {
     return false;

pnpm-lock.yaml

@@ -244,6 +244,8 @@ importers:
 
   extensions/anthropic: {}
 
+  extensions/azure-foundry: {}
+
   extensions/bluebubbles:
     dependencies:
       zod: