feat: add diagnostic interview loop

internal/workflows/runner_test.go

@@ -6,7 +6,7 @@ import (
 	"testing"
 )
 
-func TestStubRunnerReturnsTypedNotImplemented(t *testing.T) {
+func TestStubRunnerDiagnoseReturnsTypedNotImplemented(t *testing.T) {
 	runner := NewStubRunner()
 
 	_, err := runner.DiagnoseJobSeeker(context.Background(), DiagnosticInput{
@@ -19,3 +19,28 @@ func TestStubRunnerReturnsTypedNotImplemented(t *testing.T) {
 		t.Fatalf("err = %v, want %v", err, ErrNotImplemented)
 	}
 }
+
+func TestStubRunnerGradesAnswer(t *testing.T) {
+	runner := NewStubRunner()
+
+	grade, err := runner.GradeInterviewAnswer(context.Background(), GradeAnswerInput{
+		QuestionID: "q-1",
+		AnswerID:   "a-1",
+		AnswerText: "Indexes can speed reads by helping the database find rows, but they add write overhead.",
+		Concepts: []ConceptRef{
+			{ID: "database-indexes", Label: "Database indexes", Track: "backend-developer"},
+		},
+	})
+	if err != nil {
+		t.Fatalf("GradeInterviewAnswer error: %v", err)
+	}
+	if grade.AnswerID != "a-1" {
+		t.Fatalf("AnswerID = %q", grade.AnswerID)
+	}
+	if len(grade.Concepts) != 1 {
+		t.Fatalf("concepts = %d, want 1", len(grade.Concepts))
+	}
+	if len(grade.Evidence) != 1 {
+		t.Fatalf("evidence = %d, want 1", len(grade.Evidence))
+	}
+}