docs(UAT_PLAYBOOK): add TC-API-3.20 through TC-API-3.24 for seed data verification

Updated UAT_PLAYBOOK.md §4.3 — new seed data verification tests.

GRO-1898: After populating extended profile fields in the UAT seed, add
test cases to verify the data is actually present and shaped correctly.
Test cases cover:
- /api/clients returns seed data
- /api/pets/{id} returns all 5 extended fields for UAT test pets
- medicalAlerts shape is correct ({type, description, severity})
- Deterministic UAT pets (Charlie = behavioral alert, Delta = skin alert)
  are verifiably populated

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

UAT_PLAYBOOK.md

@@ -103,6 +103,18 @@ GroomBook API is a Hono-based REST service (TypeScript/Node.js) powering the pet
 | TC-API-3.18 | Get pet profile summary — visitCount returns full count | GET /api/pets/{id}/profile-summary with 2+ completed appointments | visitCount >= 2 (not capped at 1) |
 | TC-API-3.19 | Get pet profile summary — upcomingAppointment excludes past | GET /api/pets/{id}/profile-summary with a past confirmed/scheduled appointment | upcomingAppointment is null (past appointments filtered by startTime >= now) |
 
+#### Seed Data Verification (GRO-1898)
+
+> As of PR #98, UAT seed data populates all 5 extended profile fields for every pet, including the 5 deterministic UAT test client pets (Alpha, Bravo, Charlie, Delta, Echo). This enables manual verification of extended profile rendering without requiring a DB reset.
+
+| # | Scenario | Steps | Expected |
+|---|----------|-------|----------|
+| TC-API-3.20 | GET /api/clients returns seed data | GET /api/clients | 200 OK, array with 1+ clients (UAT seed creates 500 + 5 deterministic UAT clients) |
+| TC-API-3.21 | GET /api/pets/{id} returns extended fields for seed pet | Pick any pet ID from UAT test clients (uat-alpha through uat-echo pet names: TestBuddy, TestMax, TestCooper, TestRocky, TestDuke) and GET /api/pets/{id} | 200 OK; coatType, temperamentScore, temperamentFlags, medicalAlerts, preferredCuts all non-null |
+| TC-API-3.22 | Verify medicalAlerts shape | GET /api/pets/{id} for any pet with non-empty medicalAlerts | medicalAlerts is an array; each entry has type, description, severity |
+| TC-API-3.23 | Verify UAT test pet Charlie has behavioral alert | GET /api/pets/{id} where name = "TestCooper" (pet for uat-charlie@groombook.dev) | medicalAlerts includes an entry with type: "behavioral", severity: "low" or "high" |
+| TC-API-3.24 | Verify UAT test pet Delta has skin alert | GET /api/pets/{id} where name = "TestRocky" (pet for uat-delta@groombook.dev) | medicalAlerts includes an entry with type: "skin" |
+
 ### 4.4 Appointment Scheduling
 
 | # | Scenario | Steps | Expected |