Address code review feedback - improve validation and slug derivation

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: Copilot

features/site-create.feature

@@ -163,6 +163,29 @@ Feature: Create a new site on a WP multisite
       """
     And the return code should be 1
 
+  Scenario: Error when numeric-only domain is provided without slug
+    Given a WP multisite subdomain install
+
+    When I try `wp site create --site-url=http://123.example.com`
+    Then STDERR should be:
+      """
+      Error: Could not derive a valid slug from the domain. Please provide --slug explicitly.
+      """
+    And the return code should be 1
+
+  Scenario: Create site with different domain in subdirectory multisite
+    Given a WP multisite subdirectory install
+
+    When I run `wp site create --site-url=http://custom.example.com/mypath/`
+    Then STDOUT should contain:
+      """
+      Success: Site 2 created:
+      """
+    And STDOUT should contain:
+      """
+      ://custom.example.com/mypath/
+      """
+
   Scenario: Preserve existing slug behavior
     Given a WP multisite subdomain install
 

src/Site_Command.php

@@ -468,15 +468,22 @@ public function create( $args, $assoc_args ) {
 					// For subdomain installs, use the first part of the domain as the base
 					$domain_parts = explode( '.', $custom_domain );
 					$base         = $domain_parts[0];
+
+					// Validate that the derived base is suitable for use as a slug
+					if ( empty( $base ) || is_numeric( $base ) ) {
+						WP_CLI::error( 'Could not derive a valid slug from the domain. Please provide --slug explicitly.' );
+					}
 				} else {
 					// For subdirectory installs, use the path as the base
 					$base = trim( $custom_path, '/' );
 					// Use the last part of the path if there are multiple segments
-					$path_parts = explode( '/', $base );
-					$base       = end( $path_parts );
-					// If base is empty (root path), generate a random one
+					if ( ! empty( $base ) ) {
+						$path_parts = explode( '/', $base );
+						$base       = $path_parts[ count( $path_parts ) - 1 ];
+					}
+					// If base is empty (root path), generate an auto slug
 					if ( empty( $base ) ) {
-						$base = 'site-' . wp_generate_password( 8, false );
+						$base = 'auto-' . time();
 					}
 				}
 			} else {