fix(mcp): add example to server name validation error message

Fixes bounty issue #1604

The error message for invalid MCP server names now includes an example
('my-server') to help users understand the expected format.

Author: factorydroid

cortex-cli/src/mcp_cmd.rs

@@ -954,7 +954,7 @@ fn validate_server_name(name: &str) -> Result<()> {
         .all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_');
 
     if !is_valid_chars {
-        bail!("invalid server name '{name}' (use ASCII letters a-z/A-Z, digits 0-9, '-', or '_')");
+        bail!("invalid server name '{name}' (use ASCII letters a-z/A-Z, digits 0-9, '-', or '_'); example: 'my-server'");
     }
 
     // Must start with a letter or underscore