feat: implement animal lifecycle events (Step 6.3)

Add 5 animal lifecycle event handlers with TDD:
- HatchRecorded: Creates hatchling animals at brood/event location
- AnimalOutcome: Records death/harvest/sold with yields, status updates
- AnimalPromoted: Sets identified flag, nickname, optionally updates sex/repro_status
- AnimalMerged: Merges animal records, creates aliases, removes merged from live roster
- AnimalStatusCorrected: Admin-only status correction with required reason

All events include:
- Projection handlers in animal_registry.py and intervals.py
- Event-animal linking in event_animals.py
- Service methods with validation in animal.py
- 51 unit tests covering event creation, projections, and validation
- E2E test #7 (harvest with yields) per spec §21.7

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

PLAN.md

@@ -235,13 +235,13 @@ Check off items as completed. Each phase builds on the previous.
 - [x] **Commit checkpoint** (282d3d0)
 
 ### Step 6.3: Animal Lifecycle Events
-- [ ] Implement HatchRecorded (creates hatchlings)
-- [ ] Implement AnimalOutcome (death/harvest/sold with yields)
-- [ ] Implement AnimalPromoted (identified=true, nickname)
-- [ ] Implement AnimalMerged (status=merged_into, aliases)
-- [ ] Implement AnimalStatusCorrected (admin-only with reason)
-- [ ] Write tests for each event type
-- [ ] Write test: E2E test #7 (harvest with yields)
+- [x] Implement HatchRecorded (creates hatchlings)
+- [x] Implement AnimalOutcome (death/harvest/sold with yields)
+- [x] Implement AnimalPromoted (identified=true, nickname)
+- [x] Implement AnimalMerged (status=merged_into, aliases)
+- [x] Implement AnimalStatusCorrected (admin-only with reason)
+- [x] Write tests for each event type
+- [x] Write test: E2E test #7 (harvest with yields)
 - [ ] **Commit checkpoint**
 
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