fix(compliance): avoid false positive on button width check when wp:button and wp-block-buttons share a line

checkButtonWidthClasses used str_contains($html, 'wp-block-button') which
matched the plural wp-block-buttons wrapper div when it appears on the same
line as the <!-- wp:button comment (correct compact inline formatting per
Elayne CLAUDE.md). Replaced with a word-boundary regex so only the singular
wp-block-button inner div triggers the class check.

Author: jasperf

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.3.1] - 2026-05-14
+
+### Fixed
+
+- `checkButtonWidthClasses`: false positive when `<!-- wp:button` appears on the same line as the outer `<div class="wp-block-buttons">` wrapper. The previous `str_contains` check matched `wp-block-buttons` as a substring of `wp-block-button`, incorrectly reporting missing `has-custom-width`/`wp-block-button__width-N` classes. Replaced with a word-boundary regex that distinguishes the singular `wp-block-button` (inner div) from the plural `wp-block-buttons` (wrapper).
+
 ## [2.3.0] - 2026-05-14
 
 ### Added

src/Compliance/Rules/BaseRules.php

@@ -262,9 +262,12 @@ private function checkButtonWidthClasses(string $content): array
             }
             $pct = (int) $m[1];
             // Scan current line and the next two for the HTML div.
+            // Use a word-boundary match to distinguish wp-block-button (inner div)
+            // from wp-block-buttons (wrapper div that may appear on the same line
+            // as the <!-- wp:button comment when compact inline formatting is used).
             for ($j = $i; $j <= $i + 2 && $j < $total; $j++) {
                 $html = $lines[$j];
-                if (!str_contains($html, 'wp-block-button')) {
+                if (!preg_match('/\bwp-block-button\b(?!s)/', $html)) {
                     continue;
                 }
                 if (!str_contains($html, 'has-custom-width') || !str_contains($html, "wp-block-button__width-{$pct}")) {