chore(06-02): download and include Action Scheduler library

- Downloaded Action Scheduler 3.9.3 from GitHub
- Placed in vendor/action-scheduler/ directory
- Included in main plugin file before other code for proper initialization
- Library will auto-initialize itself when required

vendor/action-scheduler/classes/WP_CLI/Action/Next_Command.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Action_Scheduler\WP_CLI\Action;
+
+// phpcs:disable WordPress.Security.EscapeOutput.OutputNotEscaped -- Escaping output is not necessary in WP CLI.
+
+use function \WP_CLI\Utils\get_flag_value;
+
+/**
+ * WP-CLI command: action-scheduler action next
+ */
+class Next_Command extends \ActionScheduler_WPCLI_Command {
+
+	/**
+	 * Execute command.
+	 *
+	 * @return void
+	 */
+	public function execute() {
+		$hook          = $this->args[0];
+		$group         = get_flag_value( $this->assoc_args, 'group', '' );
+		$callback_args = get_flag_value( $this->assoc_args, 'args', null );
+		$raw           = (bool) get_flag_value( $this->assoc_args, 'raw', false );
+
+		if ( ! empty( $callback_args ) ) {
+			$callback_args = json_decode( $callback_args, true );
+		}
+
+		if ( $raw ) {
+			\WP_CLI::line( as_next_scheduled_action( $hook, $callback_args, $group ) );
+			return;
+		}
+
+		$params = array(
+			'hook'    => $hook,
+			'orderby' => 'date',
+			'order'   => 'ASC',
+			'group'   => $group,
+		);
+
+		if ( is_array( $callback_args ) ) {
+			$params['args'] = $callback_args;
+		}
+
+		$params['status'] = \ActionScheduler_Store::STATUS_RUNNING;
+		// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_var_export
+		\WP_CLI::debug( 'ActionScheduler()::store()->query_action( ' . var_export( $params, true ) . ' )' );
+
+		$store     = \ActionScheduler::store();
+		$action_id = $store->query_action( $params );
+
+		if ( $action_id ) {
+			echo $action_id;
+			return;
+		}
+
+		$params['status'] = \ActionScheduler_Store::STATUS_PENDING;
+		// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_var_export
+		\WP_CLI::debug( 'ActionScheduler()::store()->query_action( ' . var_export( $params, true ) . ' )' );
+
+		$action_id = $store->query_action( $params );
+
+		if ( $action_id ) {
+			echo $action_id;
+			return;
+		}
+
+		\WP_CLI::warning( 'No matching next action.' );
+	}
+
+}