chore: add Rush change description

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

Author: rushbot

common/changes/@microsoft/rush/native-private-members_2026-09-06-18-31.json

@@ -0,0 +1,9 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/rush",
+      "comment": "Use ECMAScript private syntax for internal class members.",
+      "type": "none"
+    }
+  ]
+}