fix(cli-guest): omit device_name from guest link refresh payload

Refresh calls POST /cli/guest with link_context only; empty device_name
was rejected by server Joi validation (422). Add omitempty and assert the
key is absent in unit and guest acceptance tests.

Co-Authored-By: Claude <noreply@anthropic.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: 3 people

pkg/hookdeck/guest.go

@@ -23,7 +23,7 @@ type GuestSigninLinkResponse struct {
 }
 
 type CreateGuestUserInput struct {
-	DeviceName  string `json:"device_name"`
+	DeviceName  string `json:"device_name,omitempty"`
 	LinkContext string `json:"link_context,omitempty"`
 }
 

pkg/login/guest_link_test.go

@@ -28,6 +28,7 @@ func TestRefreshGuestSigninLink_updatesProfileOnSuccess(t *testing.T) {
 			var input map[string]string
 			require.NoError(t, json.NewDecoder(r.Body).Decode(&input))
 			require.Equal(t, "signup", input["link_context"])
+			require.NotContains(t, input, "device_name")
 			body, err := json.Marshal(map[string]string{
 				"id":   "usr_guest_refresh",
 				"key":  "hk_test_guest_refresh_key12",

test/acceptance/guest_login_acceptance_test.go

@@ -158,6 +158,7 @@ func TestGuestLoginDefaultClaimGuestAcceptance(t *testing.T) {
 			var payload map[string]interface{}
 			require.NoError(t, json.NewDecoder(r.Body).Decode(&payload))
 			require.Equal(t, "signup", payload["link_context"])
+			require.NotContains(t, payload, "device_name")
 
 			body, encErr := json.Marshal(map[string]string{
 				"id":   "usr_guest_accept",