Fix child theme activation failure on subsequent runs with different slug and name

[Copilot]

WordPress caches theme metadata in transients and directory listings. When wp scaffold child-theme --activate creates a theme, the cache isn't refreshed before activation. First run succeeds because no cache exists yet. Subsequent runs fail with "theme directory does not exist" because WordPress reads stale cache.

Changes

• Added refresh_theme_cache() method that clears theme_roots transient and rebuilds directory cache via delete_site_transient() and search_theme_directories(true)
• Called before activation/enablement in both --activate and --enable-network code paths
• Added test scenario reproducing the bug: create child theme with --activate, delete it, recreate with same command

if ( Utils\get_flag_value( $assoc_args, 'activate' ) ) {
    $this->refresh_theme_cache();
    WP_CLI::run_command( [ 'theme', 'activate', $theme_slug ] );
}

The issue manifests when theme_slug differs from theme_name (e.g., slug: first-run, name: First Run Name) because WordPress theme lookups depend on accurate cache state.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>--activate fails after running second time if theme_slug and theme_name are different.</issue_title>
<issue_description>## Bug Report

• Yes, I reviewed the contribution guidelines.
• Yes, more specifically, I reviewed the guidelines on how to write clear bug reports.

Describe the current, buggy behavior
Run the following commands in order:

$ vendor/bin/wp scaffold child-theme first_run --parent_theme=twentytwenty --theme_name="first_run_name" --activate --path=../../
Success: Created '/srv/www/wordpress-one/public_html/wp-cli-dev/scaffold-command/../../wp-content/themes/first_run'.
Success: Switched to 'first_run_name' theme.

$ rm -rf ../../wp-content/themes/first_run/
$ wp theme activate twentytwenty

$ vendor/bin/wp scaffold child-theme first_run --parent_theme=twentytwenty --theme_name="first_run_name" --activate --path=../../
Success: Created '/srv/www/wordpress-one/public_html/wp-cli-dev/scaffold-command/../../wp-content/themes/first_run'.
Error: The theme directory "first_run" does not exist.

During the second run the command incorrectly looks for first_run instead of first_run_name to switch to.

Describe what you would expect as the correct outcome

I would expect the server to switch to the correct theme.

Let us know what environment you are running this on

$ vendor/bin/wp cli info
OS:	Linux 5.4.0-91-generic wp-cli/scaffold-command#102-Ubuntu SMP Fri Nov 5 16:31:28 UTC 2021 x86_64
Shell:	/bin/bash
PHP binary:	/usr/bin/php
PHP version:	7.4.29
php.ini used:	/etc/php/7.4/cli/php.ini
MySQL binary:	/usr/bin/mysql
MySQL version:	mysql  Ver 15.1 Distrib 10.5.16-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2
SQL modes:	STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
WP-CLI root dir:	/srv/www/wordpress-one/public_html/wp-cli-dev/wp-cli
WP-CLI vendor dir:	/srv/www/wordpress-one/public_html/wp-cli-dev/wp-cli/vendor
WP_CLI phar path:	
WP-CLI packages dir:	/home/vagrant/.wp-cli/packages/
WP-CLI global config:	
WP-CLI project config:	/srv/www/wordpress-one/public_html/wp-cli-dev/scaffold-command/wp-cli.yml
WP-CLI version:	2.7.0-alpha

Provide a possible solution

Provide additional context/Screenshots
Is partially related to #251 as @michaelandre0 already spotted this and I ran into the same situation fixing the path issue. </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes --activate fails after running second time if theme_slug and theme_name are different. #306

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