fix(tasks): return ErrNativeTaskNotFound from UpdateNativeTask on stale id

HandleWidgetTaskUpdate now returns 404 instead of silently succeeding
when the widget's cached task id no longer exists, matching every
other native_tasks mutator's checkRowsAffected pattern.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VTUSAEKfsPc6WGDq45yPHD

3 files changed, 25 insertions, 2 deletions

diff --git a/internal/handlers/widget.go b/internal/handlers/widget.go
index 15ef3b2..b8c3aa9 100644
--- a/internal/handlers/widget.go
+++ b/internal/handlers/widget.go
@@ -473,6 +473,10 @@ func (h *Handler) HandleWidgetTaskUpdate(w http.ResponseWriter, r *http.Request)
 		return
 	}
 	if err := h.store.UpdateNativeTask(req.ID, req.Title, req.Description); err != nil {
+		if errors.Is(err, store.ErrNativeTaskNotFound) {
+			http.Error(w, "task not found", http.StatusNotFound)
+			return
+		}
 		http.Error(w, "failed to update task", http.StatusInternalServerError)
 		return
 	}
diff --git a/internal/handlers/widget_test.go b/internal/handlers/widget_test.go
index 35c21e2..95f5264 100644
--- a/internal/handlers/widget_test.go
+++ b/internal/handlers/widget_test.go
@@ -924,6 +924,21 @@ func TestHandleWidgetTaskUpdate_UpdatesTitleAndDescription(t *testing.T) {
 	}
 }
 
+func TestHandleWidgetTaskUpdate_UnknownID_Returns404(t *testing.T) {
+	s, cleanup := setupTestDB(t)
+	defer cleanup()
+	h := &Handler{store: s}
+
+	body := `{"id":"does-not-exist","title":"New title","description":""}`
+	req := httptest.NewRequest("POST", "/api/widget/task/update", strings.NewReader(body))
+	w := httptest.NewRecorder()
+	http.HandlerFunc(h.HandleWidgetTaskUpdate).ServeHTTP(w, req)
+
+	if w.Code != http.StatusNotFound {
+		t.Errorf("expected 404 for an unknown task id, got %d", w.Code)
+	}
+}
+
 func TestHandleWidgetTaskRecurrence_SetsPattern(t *testing.T) {
 	s, cleanup := setupTestDB(t)
 	defer cleanup()
diff --git a/internal/store/native_tasks.go b/internal/store/native_tasks.go
index d4cc896..3bd87cb 100644
--- a/internal/store/native_tasks.go
+++ b/internal/store/native_tasks.go
@@ -125,12 +125,16 @@ func (s *Store) CreateNativeTask(task models.Task) error {
 }
 
 // UpdateNativeTask updates a native task's content and description.
+// Returns ErrNativeTaskNotFound if id doesn't match any row.
 func (s *Store) UpdateNativeTask(id, content, description string) error {
-	_, err := s.db.Exec(`
+	result, err := s.db.Exec(`
 		UPDATE native_tasks SET content = ?, description = ?, updated_at = CURRENT_TIMESTAMP
 		WHERE id = ?
 	`, content, description, id)
-	return err
+	if err != nil {
+		return err
+	}
+	return checkRowsAffected(result)
 }
 
 // UpdateNativeTaskDescription updates only a native task's description, leaving content untouched.