docs: add note that ssh/cp require dev-os flag

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

Author: h4x3rotab

phala-cloud/references/phala-cloud-cli/phala/overview.mdx

@@ -65,6 +65,10 @@ phala cvms get
 | [`ssh`](/phala-cloud/references/phala-cloud-cli/phala/ssh) | Connect to a CVM via SSH |
 | [`cp`](/phala-cloud/references/phala-cloud-cli/phala/cp) | Copy files to/from a CVM via SCP |
 
+<Note>
+SSH and SCP access require deploying with the `--dev-os` flag. See [Enable SSH Access](/phala-cloud/networking/enable-ssh-access) for details.
+</Note>
+
 ### Docker Integration
 
 | Command | Description |