Clarify Kubernetes Agent naming restrictions

doc/user/clusters/agent/install/index.md

@@ -56,6 +56,8 @@ In your repository, add the Agent configuration file under:
 .gitlab/agents/<agent-name>/config.yaml
 ```
 
+Make sure that `<agent-name>` conforms to the [Agent's naming format](https://gitlab.com/gitlab-org/cluster-integration/gitlab-agent/-/blob/master/doc/identity_and_auth.md#agent-identity-and-name).
+
 Your `config.yaml` file specifies all configurations of the Agent, such as:
 
 - The manifest projects to synchronize.

doc/user/clusters/agent/repository.md

@@ -23,16 +23,18 @@ The Agent bootstraps with the GitLab installation URL and an authentication toke
 and you provide the rest of the configuration in your repository, following
 Infrastructure as Code (IaaC) best practices.
 
-A minimal repository layout looks like this, with `my_agent_1` as the name
+A minimal repository layout looks like this, with `my-agent-1` as the name
 of your Agent:
 
 ```plaintext
 |- .gitlab
     |- agents
-       |- my_agent_1
+       |- my-agent-1
           |- config.yaml
 ```
 
+Make sure that `<agent-name>` conforms to the [Agent's naming format](https://gitlab.com/gitlab-org/cluster-integration/gitlab-agent/-/blob/master/doc/identity_and_auth.md#agent-identity-and-name).
+
 ## Synchronize manifest projects **(PREMIUM)**
 
 Your `config.yaml` file contains a `gitops` section, which contains a `manifest_projects`