feat: acceptance_criteria per story task in elaboration and approval

Add AcceptanceCriteria field to elaboratedStoryTask struct, update
buildStoryElaboratePrompt schema and rules, pass the value through
handleApproveStory into task.Task, and add a test verifying the
field is persisted on approved story tasks.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/internal/api/stories_test.go b/internal/api/stories_test.go
index 342840b..f43ad86 100644
--- a/internal/api/stories_test.go
+++ b/internal/api/stories_test.go
@@ -258,6 +258,55 @@ func TestHandleStoryApprove_SetsRepositoryURL(t *testing.T) {
 	}
 }
 
+func TestApproveStory_AcceptanceCriteriaStored(t *testing.T) {
+	srv, store := testServer(t)
+
+	proj := &task.Project{
+		ID: "ac-proj", Name: "test", RemoteURL: "https://github.com/x/y",
+		Type: "web", DeployScript: "",
+	}
+	store.CreateProject(proj)
+
+	body := `{
+		"name": "AC Story",
+		"branch_name": "story/ac-test",
+		"project_id": "ac-proj",
+		"tasks": [
+			{
+				"name": "Add feature",
+				"instructions": "implement the thing",
+				"acceptance_criteria": "run go test ./... and verify all pass",
+				"subtasks": []
+			}
+		],
+		"validation": {"type": "test", "steps": [], "success_criteria": "tests pass"}
+	}`
+	req := httptest.NewRequest("POST", "/api/stories/approve", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	srv.mux.ServeHTTP(w, req)
+
+	if w.Code != http.StatusCreated {
+		t.Fatalf("expected 201, got %d: %s", w.Code, w.Body.String())
+	}
+
+	var resp struct {
+		TaskIDs []string `json:"task_ids"`
+	}
+	json.NewDecoder(w.Body).Decode(&resp)
+	if len(resp.TaskIDs) == 0 {
+		t.Fatal("expected task_ids in response")
+	}
+
+	tk, err := store.GetTask(resp.TaskIDs[0])
+	if err != nil {
+		t.Fatalf("GetTask: %v", err)
+	}
+	if tk.AcceptanceCriteria != "run go test ./... and verify all pass" {
+		t.Errorf("expected acceptance criteria stored on task, got %q", tk.AcceptanceCriteria)
+	}
+}
+
 func TestHandleStoryDeploymentStatus(t *testing.T) {
 	srv, store := testServer(t)