feat: seamless auto-continue on Joomla Update after pre-update backup

After the full-screen pre-update backup returns to the Joomla Update
confirm page (layout=update&is_backed_up=1), inject a small script that
ticks Joomla's 'I have taken a backup' checkbox (#joomlaupdate-confirm-
backup) and clicks the Install button (.emptystate-btnadd) so the update
continues automatically — no second manual click. Injected via
onBeforeCompileHead, super-user only, gated on backup_before_update.

Claude-Session: https://claude.ai/code/session_01WbGBN9VyRK61zczYWcCQ2i

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## [Unreleased]
 
 ### Fixed
+- Pre-update backup on the **Joomla Update** page is now **seamless** (Akeeba-style): after the full-screen backup runs, the plugin auto-ticks Joomla's "I have taken a backup" checkbox and clicks Install, so the update continues automatically instead of stopping for a second manual click.
 - Pre-update full-screen backup now actually fires on the **Joomla Update** page. The "Install the update" button posts to `option=com_joomlaupdate&layout=update` (Joomla's confirm/updating page) — carrying **only `layout=update`**, no `view`/`task` — so the previous match on `view=update`/`update.install` never triggered. The plugin now intercepts `layout=update` (as well as `view=update` and the legacy `update.install`) and returns the browser there flagged `is_backed_up=1`.
 
 ### Added

source/packages/plg_system_mokosuitebackup/src/Extension/MokoSuiteBackup.php

@@ -170,6 +170,25 @@ final class MokoSuiteBackup extends CMSPlugin implements SubscriberInterface
 
 		$input = $app->getInput();
 
+		// Joomla core update: after the pre-update backup returns to the confirm
+		// page (layout=update&is_backed_up=1), auto-check Joomla's "I have a
+		// backup" box and click Install so the update continues seamlessly
+		// (Akeeba-style) instead of stopping for a second manual click.
+		if ($input->getCmd('option', '') === 'com_joomlaupdate') {
+			if ($input->getCmd('layout', '') === 'update'
+				&& (int) ComponentHelper::getParams('com_mokosuitebackup')->get('backup_before_update', 0)) {
+				$user = $app->getIdentity();
+				$doc  = $app->getDocument();
+
+				if ($user && !$user->guest && $user->authorise('core.admin') && $doc instanceof HtmlDocument) {
+					$doc->getWebAssetManager()->useScript('core');
+					$doc->addScriptDeclaration($this->joomlaUpdateAutoContinueScript());
+				}
+			}
+
+			return;
+		}
+
 		if ($input->getCmd('option', '') !== 'com_installer') {
 			return;
 		}
@@ -226,6 +245,30 @@ final class MokoSuiteBackup extends CMSPlugin implements SubscriberInterface
 		$doc->addScript(Uri::root(true) . '/media/plg_system_mokosuitebackup/js/installer-backup.js', [], ['defer' => true]);
 	}
 
+	/**
+	 * Inline JS for the Joomla Update confirm page. When we return there after
+	 * the pre-update backup (is_backed_up=1), it ticks Joomla's "I have taken a
+	 * backup" checkbox and clicks the Install button (.emptystate-btnadd) so the
+	 * update proceeds automatically — seamless, no second manual click.
+	 */
+	private function joomlaUpdateAutoContinueScript(): string
+	{
+		return <<<'JS'
+(function () {
+'use strict';
+if (new URLSearchParams(window.location.search).get('is_backed_up') !== '1') { return; }
+var go = function () {
+	var chk  = document.getElementById('joomlaupdate-confirm-backup');
+	var wrap = document.getElementById('joomlaupdate-wrapper');
+	var btn  = (wrap && wrap.querySelector('.emptystate-btnadd')) || document.querySelector('.emptystate-btnadd');
+	if (chk) { chk.checked = true; chk.dispatchEvent(new Event('change', { bubbles: true })); }
+	if (btn) { btn.classList.remove('disabled'); window.setTimeout(function () { btn.click(); }, 400); }
+};
+if (document.readyState === 'loading') { document.addEventListener('DOMContentLoaded', go); } else { go(); }
+})();
+JS;
+	}
+
 	/**
 	 * Send a Joomla core update through the full-screen backup page BEFORE the
 	 * update applies (Akeeba-style), so no backup runs synchronously inside the