docs(GRO-1470): add UAT test cases for pet profile API persistence

Add §5.23 covering:
- API persistence (page reload verification)
- Save error state (form stays open on failure)
- Saving indicator (spinner while in-flight)

Updated UAT_PLAYBOOK.md §5.23

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

UAT_PLAYBOOK.md

@@ -275,6 +275,14 @@ export const { signIn, signOut, useSession, changePassword } = authClient;
 | TC-WEB-5.22.6 | Size and coat persisted | Save pet with size + coat, edit again | Both fields retain their selected values |
 | TC-WEB-5.22.7 | Clear size | Select size, then clear back to default | Size cleared on save |
 
+### 5.23 Pet Profile — API Persistence & Save UX (GRO-1470)
+
+| # | Scenario | Steps | Expected |
+|---|----------|-------|----------|
+| TC-WEB-5.23.1 | Save pet — API persistence | Edit a pet, change a field (e.g. coat type), click Save, reload the page | Changed field retained after reload (proves PATCH round-trip to server) |
+| TC-WEB-5.23.2 | Save pet — error state | Trigger an API save failure (e.g. network error) | Error message displayed; edit form stays open; no data cleared |
+| TC-WEB-5.23.3 | Save pet — saving indicator | Click Save | Spinner/indicator shown while request is in flight; form controls disabled |
+
 ## 6. Pass/Fail Criteria
 
 **Pass:**