feat(llm): client interface and fake test double

internal/llm/fake_test.go

@@ -0,0 +1,21 @@
+package llm
+
+import (
+	"context"
+	"testing"
+)
+
+func TestFakeClient(t *testing.T) {
+	f := &Fake{VisionResp: "hello", TranscribeResp: "spoken"}
+	got, err := f.Vision(context.Background(), "p", []Image{{MediaType: "image/png", Data: []byte{1}}}, Options{})
+	if err != nil || got != "hello" {
+		t.Fatalf("vision got %q err %v", got, err)
+	}
+	if len(f.VisionCalls) != 1 || f.VisionCalls[0].Prompt != "p" {
+		t.Fatalf("vision call not recorded: %+v", f.VisionCalls)
+	}
+	tr, err := f.Transcribe(context.Background(), []byte{1}, "audio.mp3", Options{Language: "en"})
+	if err != nil || tr != "spoken" {
+		t.Fatalf("transcribe got %q err %v", tr, err)
+	}
+}