Add atomic activity ingestion validation script

Validates core ingestion with four test scenarios:
- Valid insert (should succeed)
- Invalid status value (should fail)
- Missing required field (should fail)
- Confirm atomic insert (should always succeed if schema-valid)
Each test outputs PASS/FAIL and error details for review.

test_validation.py

@@ -0,0 +1,56 @@
+"""
+Validation script: Runs schema-compliant inserts, error cases, and prints results for atomic activity ingestion function.
+"""
+from activity_ingestion import atomic_append_activity
+import os
+
+def print_test_result(test_name, result):
+    status = 'PASS' if result['success'] else 'FAIL'
+    print(f'[{status}] {test_name}')
+    if result['error']:
+        print(f'  Error: {result["error"]}')
+    else:
+        print(f'  Commit Hash: {result.get("commit_hash")}, Request ID: {result.get("request_id")}')
+
+def test_all():
+    # Clean up before test for atomicity validation
+    if os.path.exists('activity_log.csv'):
+        os.rename('activity_log.csv', 'activity_log.csv.bak')
+    
+    valid_rec = {
+        'agent_id': 'validation_agent',
+        'activity_type': 'ingest',
+        'entity_id': 'entity_001',
+        'status': 'success',
+        'notes': 'Valid activity example',
+        'context': 'Validation test - success'
+    }
+    invalid_rec = {
+        'agent_id': 'validation_agent',
+        'activity_type': 'ingest',
+        'entity_id': 'entity_002',
+        'status': 'not_valid', # invalid
+        'notes': 'Should fail',
+        'context': 'Validation test - error'
+    }
+    missing_field = {
+        'agent_id': 'validation_agent',
+        'activity_type': 'ingest',
+        # 'entity_id' missing
+        'status': 'success',
+        'notes': 'Missing field',
+        'context': 'Validation test - missing'
+    }
+    print('Running validation tests...')
+    print_test_result('Valid record insert', atomic_append_activity('activity_log.csv', valid_rec))
+    print_test_result('Invalid status value', atomic_append_activity('activity_log.csv', invalid_rec))
+    print_test_result('Missing required field', atomic_append_activity('activity_log.csv', missing_field))
+    print('Re-inserting valid to confirm atomicity:')
+    print_test_result('Second valid insert', atomic_append_activity('activity_log.csv', valid_rec))
+    
+    if os.path.exists('activity_log.csv.bak'):
+        os.remove('activity_log.csv')
+        os.rename('activity_log.csv.bak', 'activity_log.csv')
+
+if __name__ == '__main__':
+    test_all()