Update relative path for jetpack-mu-wpcom (#41861)

* Fix: Ensure correct MD5 hash lookup for script translation files

A recent change renamed `vendor/` to `jetpack_vendor/`, causing mismatches
in generated MD5 hashes and resulting in missing translation JSON files.
#41185

projects/packages/jetpack-mu-wpcom/changelog/fix-update-relative-path-for-jetpack-mu-wpcom

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+i18n: fix missing script translations

projects/packages/jetpack-mu-wpcom/src/class-jetpack-mu-wpcom.php

@@ -27,6 +27,8 @@ public static function init() {
 		if ( did_action( 'jetpack_mu_wpcom_initialized' ) ) {
 			return;
 		}
+		// Apply temporary fix for translation path MD5 mismatch due to vendor -> jetpack_vendor change in https://github.com/Automattic/jetpack/pull/41185
+		add_filter( 'load_script_textdomain_relative_path', array( __CLASS__, 'fix_translation_relative_path_mismatch_wpcom_jetpack' ), 20, 2 );
 
 		// Shared code for src/features.
 		require_once self::PKG_DIR . 'src/common/index.php'; // phpcs:ignore WordPressVIPMinimum.Files.IncludingFile.NotAbsolutePath
@@ -89,6 +91,25 @@ public static function init() {
 		do_action( 'jetpack_mu_wpcom_initialized' );
 	}
 
+	/**
+	 * Fixes translation file path MD5 mismatches caused by vendor -> jetpack_vendor migration.
+	 *
+	 * WordPress generates the translation file's MD5 hash based on the script's relative path.
+	 * Since the path structure changed, we rewrite `jetpack_vendor/` back to `vendor/` before hashing.
+	 *
+	 * @param string|false $relative The relative script path (before MD5 hashing).
+	 * @param string       $src     The script's original source path (unused).
+	 * @return string|false Updated relative path that keeps WordPress's MD5 hash consistent.
+	 */
+	public static function fix_translation_relative_path_mismatch_wpcom_jetpack( $relative, $src ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+		if ( $relative && str_contains( $relative, 'jetpack_vendor/automattic/jetpack-mu-wpcom/src/build/' ) ) {
+			// Rewrite "jetpack_vendor/" back to the original "vendor/" to maintain MD5 compatibility
+			$relative = str_replace( 'jetpack_vendor/', 'vendor/', $relative );
+		}
+
+		return $relative;
+	}
+
 	/**
 	 * Load features that don't need any special loading considerations.
 	 */

projects/plugins/mu-wpcom-plugin/changelog/fix-update-relative-path-for-jetpack-mu-wpcom

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+i18n: fix missing script translations

projects/plugins/wpcomsh/changelog/fix-update-relative-path-for-jetpack-mu-wpcom

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+i18n: fix missing script translations