chore(cas): inline single-use test helper

Assisted-by: Claude Code
Signed-off-by: Miguel Martinez Trivino <miguel@chainloop.dev>

Chainloop-Trace-Sessions: 0c60a332-e0f1-4c2b-94ae-533467e52f5c

Author: migmartri

app/artifact-cas/internal/service/auditor_test.go

@@ -119,10 +119,10 @@ func TestAuditDispatcherDispatch(t *testing.T) {
 			// must never panic nor return an error
 			tc.dispatcher.Dispatch(tc.entry, tc.claims)
 
-			fake, ok := publisherAsFake(tc.dispatcher)
-			if !ok {
+			if tc.dispatcher == nil || tc.dispatcher.publisher == nil {
 				return
 			}
+			fake := tc.dispatcher.publisher.(*fakePublisher)
 
 			require.Len(t, fake.published, tc.wantPublished)
 			if tc.wantPublished == 0 {
@@ -161,15 +161,6 @@ func TestAuditDispatcherShouldEmit(t *testing.T) {
 	}
 }
 
-func publisherAsFake(d *AuditDispatcher) (*fakePublisher, bool) {
-	if d == nil || d.publisher == nil {
-		return nil, false
-	}
-
-	fake, ok := d.publisher.(*fakePublisher)
-	return fake, ok
-}
-
 // artifactEventInfo mirrors the action info payload of CAS artifact events for assertions
 type artifactEventInfo struct {
 	Digest      string `json:"digest"`