feat(goctl/rpc): support external proto imports with cross-package ty… (#5472)

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

tools/goctl/rpc/example/10-streaming/README.md

@@ -0,0 +1,66 @@
+# Example 10: Streaming RPC
+
+This example demonstrates all three gRPC streaming patterns: server streaming, client streaming, and bidirectional streaming.
+
+## Proto Definition
+
+`stream.proto` defines three RPC methods demonstrating each streaming pattern.
+
+The `go_package` uses a full module path:
+
+```protobuf
+option go_package = "example.com/demo/pb";
+```
+
+## Generation Commands
+
+First, initialize the output directory with a `go.mod`:
+
+```bash
+mkdir -p output && cd output && go mod init example.com/demo && cd ..
+```
+
+Then generate the code:
+
+```bash
+goctl rpc protoc stream.proto \
+  --go_out=output \
+  --go-grpc_out=output \
+  --zrpc_out=output \
+  --go_opt=module=example.com/demo \
+  --go-grpc_opt=module=example.com/demo \
+  --module=example.com/demo \
+  -I .
+```
+
+Generated directory structure:
+
+```
+output/
+├── etc
+│   └── streamsvc.yaml
+├── go.mod
+├── internal
+│   ├── config
+│   │   └── config.go
+│   ├── logic
+│   │   ├── bidistreamlogic.go
+│   │   ├── clientstreamlogic.go
+│   │   └── serverstreamlogic.go
+│   ├── server
+│   │   └── streamserviceserver.go
+│   └── svc
+│       └── servicecontext.go
+├── pb
+│   ├── stream.pb.go
+│   └── stream_grpc.pb.go
+├── streamservice
+│   └── streamservice.go
+└── streamsvc.go
+```
+
+## Key Points
+
+- Supports three streaming patterns: server streaming (`stream` on response), client streaming (`stream` on request), and bidirectional streaming (`stream` on both).
+- goctl generates separate logic files for each streaming RPC method.
+- Streaming client code is not auto-generated; use the gRPC client directly.