feat(go): report the compiled routing backend

bindings/go/README.md

@@ -70,6 +70,7 @@ Import `encoding/json` and
 
 The backend is selected at build time: `cgo` with `switchyard_native` uses the
 native library; other builds use WASM. Both use `New(config)` and the same routing API.
+Call `Backend()` to report `"native"` or `"wasm"` without creating a router.
 
 Supply the model groups needed by the configured algorithm. Composite needs
 `any` for eligible answer targets, plus `capable`, `efficient`, and `judge`.

bindings/go/backend_native.go

@@ -26,6 +26,9 @@ import (
 	"unsafe"
 )
 
+// Backend returns the compiled routing backend: "native" or "wasm".
+func Backend() string { return "native" }
+
 type nativeBackend struct {
 	mu  sync.RWMutex
 	ptr *C.SyRouter

bindings/go/backend_native_test.go

@@ -0,0 +1,14 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//go:build cgo && switchyard_native
+
+package switchyard
+
+import "testing"
+
+func TestBackend(t *testing.T) {
+	if got := Backend(); got != "native" {
+		t.Fatalf("Backend() = %q, want native", got)
+	}
+}

bindings/go/backend_wazero.go

@@ -18,6 +18,9 @@ import (
 	"time"
 )
 
+// Backend returns the compiled routing backend: "native" or "wasm".
+func Backend() string { return "wasm" }
+
 type wasmBackend struct {
 	runtime   *wasmRuntime
 	slots     []*wasmSlot

bindings/go/wasm_test.go

@@ -83,6 +83,12 @@ func TestWasmCancellationBeforeOutcome(t *testing.T) {
 	}
 }
 
+func TestBackend(t *testing.T) {
+	if got := Backend(); got != "wasm" {
+		t.Fatalf("Backend() = %q, want wasm", got)
+	}
+}
+
 // Parent and child identities must share the guest that owns their session state.
 func TestWasmSessionAffinity(t *testing.T) {
 	backend := &wasmBackend{slots: []*wasmSlot{{}, {}}}