chore: import upstream snapshot with attribution

examples/grpc-interop/README.md

@@ -0,0 +1,66 @@
+# gRPC Interop Example
+
+This example shows that **any standard gRPC client** can call a go-micro service — no go-micro SDK required on the client side.
+
+The server is a normal go-micro service using the gRPC transport. The client is a plain `google.golang.org/grpc` client with no go-micro imports.
+
+## How it works
+
+go-micro's gRPC server uses a [`grpc.UnknownServiceHandler`](https://pkg.go.dev/google.golang.org/grpc#UnknownServiceHandler) that catches all incoming requests and routes them by parsing the standard gRPC method path (`/package.Service/Method`). This means any language with gRPC support (Python, Java, Rust, etc.) can call go-micro services using generated protobuf stubs.
+
+## Running
+
+Start the server:
+
+```bash
+cd examples/grpc-interop
+go run ./server/
+```
+
+In another terminal, call it with the standard gRPC client:
+
+```bash
+cd examples/grpc-interop
+go run ./client/ --name Alice
+# Response: Hello Alice
+```
+
+## Calling from other languages
+
+Generate stubs from `proto/greeter.proto` in your language of choice and point them at `localhost:50051`. For example, with Python:
+
+```bash
+pip install grpcio-tools
+python -m grpc_tools.protoc -Iproto --python_out=. --grpc_python_out=. proto/greeter.proto
+```
+
+```python
+import grpc
+import greeter_pb2
+import greeter_pb2_grpc
+
+channel = grpc.insecure_channel("localhost:50051")
+stub = greeter_pb2_grpc.GreeterStub(channel)
+
+response = stub.Hello(greeter_pb2.HelloRequest(name="Alice"))
+print(response.message)  # Hello Alice
+```
+
+## Key points
+
+- The go-micro server registers handlers via `pb.RegisterGreeterHandler()`
+- The standard gRPC client uses stubs generated by `protoc-gen-go-grpc`
+- Both share the same `.proto` file — that's the contract
+- The server uses protobuf encoding on the wire, same as any gRPC service
+- Service discovery (mDNS, consul, etc.) is only needed for go-micro-to-go-micro calls; direct gRPC clients connect by address
+
+## Regenerating proto stubs
+
+```bash
+protoc --go_out=. --go_opt=paths=source_relative \
+       --go-grpc_out=. --go-grpc_opt=paths=source_relative \
+       --micro_out=. --micro_opt=paths=source_relative \
+       proto/greeter.proto
+```
+
+Requires `protoc-gen-go`, `protoc-gen-go-grpc`, and `protoc-gen-micro`.