Fix Mentra nested Responses endpoints

vendor/mentra-provider/README.md

@@ -0,0 +1,11 @@
+# mentra-provider
+
+`mentra-provider` is Mentra's publishable provider-core crate.
+
+It contains provider-neutral request, response, model, streaming, and tool
+schema types that can be reused without depending on the full Mentra runtime.
+
+For most application code, depend on
+[`mentra`](https://crates.io/crates/mentra) instead. The `mentra` crate
+re-exports these provider-core types and adds the runtime, tooling,
+persistence, and collaboration layers.