fix(optimize): replace load event listeners in JS Delay mode

[faisalahammad]

Summary

Fixes issue where scripts delayed by LiteSpeed Cache (optm-js_defer = 2 / JS Delay mode) attaching event listeners to load event fail to execute because the native browser load event fires before delayed scripts run.

Fixes #629

Changes

src/optimize.cls.php

Before:

if ($file_type == 'js') {
    $con = str_replace('DOMContentLoaded', 'DOMContentLiteSpeedLoaded', $con);
    // $con = str_replace( 'addEventListener("load"', 'addEventListener("litespeedLoad"', $con );
}

After:

if ($file_type == 'js') {
    $con = $this->_replace_js_events( $con );
}

private function _replace_js_events( $con ) {
    $con = str_replace( 'DOMContentLoaded', 'DOMContentLiteSpeedLoaded', $con );
    $con = preg_replace( '/(?<!\.)\b(window\.|document\.)?addEventListener\(\s*([\'"])load\2/', 'addEventListener($2DOMContentLiteSpeedLoaded$2', $con );
    $con = preg_replace( '/((?:$|jQuery)\(\s*(?:window|document)\s*\)\s*\.on\(\s*)([\'"])load(?:\.[\w-]+)?\2/', '$1$2DOMContentLiteSpeedLoaded$2', $con );
    $con = preg_replace( '/\bwindow\.onload\s*=/', 'window.addEventListener("DOMContentLiteSpeedLoaded",', $con );
    return $con;
}

Why: Replaces DOMContentLoaded and load event listeners on window and document with DOMContentLiteSpeedLoaded in JS Delay mode. Preserves element-level listeners (such as image load or XMLHttpRequest load listeners).

Testing

Test 1: JS Delay Event Listener Replacement

1. Enable JS Delay (optm-js_defer = 2) in LiteSpeed Cache settings.
2. Load a page containing delayed scripts with window.addEventListener('load', ...) or $(window).on('load', ...) or window.onload = ....
3. Interact with the page to trigger JS delay loading.
   Result: load event handlers execute cleanly upon dispatch of DOMContentLiteSpeedLoaded.

Test 2: Element-Level Load Listeners

1. Inspect image load listeners (img.addEventListener('load', ...)).
   Result: Element-level image and XHR load listeners are preserved untouched and function as expected.

[timotei-litespeed]

@faisalahammad please make sure there is just 1 change per PR. I see multiple changes(different bugs) added.

[faisalahammad]

Updated PR to contain only 1 change for JS Delay load event listener replacement. Removed all other unrelated commits.

[timotei-litespeed]

@faisalahammad I will look over the code on Monday. Thank you

[faisalahammad]

Confirmed. Kept this PR to one change. Also fixed the new method @SInCE to 8.0 and added an 8.0 changelog entry.

[faisalahammad]

Fixed the JS Delay exclusion regression in b02282e. The litespeed_optm_cssjs callback now accepts the third source argument and skips load-event rewriting when the source matches cfg_js_defer_exc. Non-JS content remains unchanged. Verified with PHP lint, PHPCS, focused exclusion/event rewrite tests, and an independent code review. No changes were made to the separate event-pattern coverage items.