test(knowledge): unbreak service test package after tag-loading change

Fixing the knowledge_create_test compile error in this branch let the
internal/application/service test package run for the first time, which
exposed two latent failures introduced when GetKnowledgeByID started
eagerly loading tags:

- GetOwningKBCreatorID went through the service-level GetKnowledgeByID
  (which now calls repo.GetKnowledgeTags); ownership resolution only
  needs the knowledge -> kb_id link, so resolve via repo.GetKnowledgeByID
  directly (tenant-scoped) and drop the extra tag query.
- createKnowledgeFileRepoStub lacked GetKnowledgeTags, which the create
  path always invokes via setAndAttachKnowledgeTags; add the stub method.

internal/application/service/knowledge.go

@@ -489,7 +489,15 @@ func (s *knowledgeService) GetKnowledgeByIDOnly(ctx context.Context, id string)
 // KB row itself is not returned so callers can't accidentally widen
 // their scope past "needed the creator id".
 func (s *knowledgeService) GetOwningKBCreatorID(ctx context.Context, knowledgeID string) (string, error) {
-	knowledge, err := s.GetKnowledgeByID(ctx, knowledgeID)
+	// Resolve via the repository directly: ownership only needs the
+	// knowledge -> kb_id link, so we deliberately skip the service-level
+	// GetKnowledgeByID (which also eagerly loads tags) to keep this lookup
+	// minimal and tenant-scoped.
+	tenantID, ok := ctx.Value(types.TenantIDContextKey).(uint64)
+	if !ok {
+		return "", werrors.NewUnauthorizedError("Tenant ID not found in context")
+	}
+	knowledge, err := s.repo.GetKnowledgeByID(ctx, tenantID, knowledgeID)
 	if err != nil {
 		return "", err
 	}

internal/application/service/knowledge_create_test.go

@@ -39,6 +39,15 @@ func (r *createKnowledgeFileRepoStub) CreateKnowledge(ctx context.Context, knowl
 	return r.createErr
 }
 
+// GetKnowledgeTags is invoked by setAndAttachKnowledgeTags after create even
+// when no tags were supplied; a fresh knowledge has none, so return empty.
+func (r *createKnowledgeFileRepoStub) GetKnowledgeTags(
+	ctx context.Context,
+	knowledgeIDs []string,
+) (map[string][]*types.KnowledgeTag, error) {
+	return map[string][]*types.KnowledgeTag{}, nil
+}
+
 type createKnowledgeFileKBServiceStub struct {
 	interfaces.KnowledgeBaseService