fix: simplify responsive breakpoint comment in admin-styles.css (issue #93) (#105)

* fix: remove redundant Responsive Styles comment in admin-styles.css (issue #93)

Removes the generic '/* Responsive Styles */' comment that was redundant
alongside the specific '/* 782px is the WordPress mobile admin breakpoint. */'
comment, per Gemini Code Assist review feedback on PR #87.

Closes #93

* fix: add missing trailing commas to fix comma-dangle lint errors

Fixes ESLint comma-dangle errors in:
- cypress.config.js (lines 15-16): missing trailing commas on
  chromeWebSecurity property and closing e2e object brace
- cypress/e2e/playground-single-site.cy.js (line 23): missing trailing
  comma on expect() message argument

Also updates eslint-plugin-cypress from ^2.15.1 to ^6.2.0 to resolve
peer dependency conflict that prevented local lint verification.

cypress/e2e/playground-single-site.cy.js

@@ -20,7 +20,7 @@ describe('WordPress Playground Single Site Tests', () => {
     cy.get('body', { timeout: 15000 }).then(($body) => {
       expect(
         $body.find('tr[data-slug="wp-plugin-starter-template-for-ai-coding"] .deactivate a').length,
-        'Starter template plugin should be present and active'
+        'Starter template plugin should be present and active',
       ).to.be.greaterThan(0);
 
       if ($body.text().includes('Plugin Toggle')) {