fix(tests): resolve 4 failing test suites and patch lodash vulnerability

Test fixes (type mismatches introduced by V&V resolution changes):
- HealthDetailedController.test.ts: replace pool/makePool with dbProbe/makeDbProbe
  to match refactored HealthDetailedDeps interface (Pool → DbProbe abstraction)
- EventPublisher.test.ts: pass all 4 required constructor args to WebhookDeliveryWorker
  mock (pool, vaultClient, redisClient, redisUrl) — was passing only 1
- MarketplaceService.test.ts: IAgent.did/didCreatedAt are string|undefined (not null);
  fix makeAgent defaults and makeAgent({did:null}) call; fix type assertion to unknown first
- OIDCTrustPolicyService.test.ts: ICreateTrustPolicyRequest.branch is string|undefined
  (not nullable); replace all branch:null with branch:undefined

Security fix:
- npm audit fix: lodash ≤4.17.23 (HIGH) → patched; 0 vulnerabilities remaining

Result: 50/50 test suites pass, 722/722 tests pass, 0 vulnerabilities

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/services/OIDCTrustPolicyService.test.ts

@@ -52,7 +52,7 @@ describe('OIDCTrustPolicyService', () => {
       const result = await service.createTrustPolicy({
         provider: 'github',
         repository: 'acme/my-repo',
-        branch: null,
+        branch: undefined,
         agentId: 'agent-001',
       });
 
@@ -66,7 +66,7 @@ describe('OIDCTrustPolicyService', () => {
         service.createTrustPolicy({
           provider: 'gitlab' as never,
           repository: 'acme/my-repo',
-          branch: null,
+          branch: undefined,
           agentId: 'agent-001',
         }),
       ).rejects.toThrow(ValidationError);
@@ -77,7 +77,7 @@ describe('OIDCTrustPolicyService', () => {
         service.createTrustPolicy({
           provider: 'github',
           repository: 'no-slash-here',
-          branch: null,
+          branch: undefined,
           agentId: 'agent-001',
         }),
       ).rejects.toThrow(ValidationError);
@@ -88,7 +88,7 @@ describe('OIDCTrustPolicyService', () => {
         service.createTrustPolicy({
           provider: 'github',
           repository: 'acme/my-repo',
-          branch: null,
+          branch: undefined,
           agentId: '',
         }),
       ).rejects.toThrow(ValidationError);
@@ -101,7 +101,7 @@ describe('OIDCTrustPolicyService', () => {
         service.createTrustPolicy({
           provider: 'github',
           repository: 'acme/my-repo',
-          branch: null,
+          branch: undefined,
           agentId: 'nonexistent',
         }),
       ).rejects.toThrow(ValidationError);