Add persistent browser auth to connector canvas

Replace Azure CLI-only authentication with InteractiveBrowserCredential, protected sign-in lifecycle endpoints, and subscription refresh after sign-in. Persist the Azure Identity cache securely across extension reloads and align connector restart guidance with the GitHub Copilot app.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

extensions/connector-namespaces/package.json

@@ -1,6 +1,6 @@
 {
   "name": "connector-namespaces",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "type": "module",
   "main": "extension.mjs",
   "description": "Browse, connect, and open MCP connectors from your Azure Connector Namespace in Sandbox.",
@@ -14,6 +14,8 @@
   ],
   "license": "MIT",
   "dependencies": {
+    "@azure/identity": "^4.13.1",
+    "@azure/identity-cache-persistence": "^1.3.0",
     "@github/copilot-sdk": "1.0.6"
   }
 }