refactor(a11y): comprehensive WCAG 2.2 AA accessibility improvements (#924)

* refactor(a11y): comprehensive WCAG 2.2 AA accessibility improvements

Add skip-to-content link, landmark regions, ARIA attributes, keyboard
navigation, focus styles, reduced-motion support, and i18n keys across
all layouts, partials, shortcodes, and JS components.

- Add skip nav link in baseof.html and id="content" on all <main> tags
- Fix 404 page lang/dir attributes and add <main> landmark
- Add aria-label to banner close, PDF iframe, search input/results
- Remove aria-hidden from back-to-top button
- Add aria-hidden to decorative external link icon
- Add role="tablist" to tabs, aria-expanded to filetree/dropdowns
- Wrap mermaid diagrams in role="img", asciinema in role="region"
- Change theme toggle <p> items to <button role="menuitem"> with
  full keyboard navigation (Arrow/Home/End/Escape)
- Add arrow-key keyboard navigation to tabs component
- Separate sidebar collapsible button from link for independent
  keyboard access with aria-expanded sync
- Sync aria-expanded on all dropdown toggles (theme, lang, navbar,
  hamburger, page context menu)
- Add aria-live search status announcements
- Add 13 new i18n keys, replace hardcoded aria-label strings
- Add prefers-reduced-motion CSS override and focus-visible base styles
- Add aria-label swap on code copy ("Copied!" feedback for AT)
- Add aria-current to active TOC links
- Wrap filetree in <ul> container for proper list semantics
- Add unique aria-label to blog "Read more" links
- Document accessibility guidelines in AGENTS.md

* feat(a11y): enhance focus styles and accessibility for various components

- Add focus-visible styles to badges, buttons, and links for improved keyboard navigation.
- Update breadcrumb, sidebar, and TOC components to include focus-visible outlines.
- Introduce new classes for focus states in the badge and tabs shortcodes.
- Ensure consistent focus styles across all interactive elements to meet WCAG 2.2 AA standards.

* feat(a11y): implement new focus-visible utilities and enhance accessibility styles

- Introduce new utility classes for focus-visible states to improve keyboard navigation.
- Update various components including badges, buttons, and search inputs to utilize new focus-visible styles.
- Refactor existing focus styles to ensure consistency and compliance with accessibility standards.
- Enhance breadcrumb, sidebar, and TOC components with updated focus-visible classes for better user experience.

* chore: add .gitattributes to collapse generated files in PR diffs

* fix: enhance accessibility and improve documentation

- Added alt attributes to images in multiple language documentation files for better accessibility.
- Updated the navbar title partial to remove unnecessary title attribute.
- Improved search input accessibility by adding autocomplete="off".
- Enhanced search partials in both navbar and sidebar with location context.
- Updated SVG icons in various components to include aria-hidden and focusable attributes for improved accessibility compliance.

* fix: improve giscus theme toggle functionality

- Updated the theme toggle options selector to use a data attribute for better specificity.
- Modified the event listener to use a setTimeout for the theme update, ensuring smoother transitions when the theme switcher is clicked.

* fix: resolve axe-core WCAG AA violations across docs pages

Add aria-labels to Hugo task list checkboxes, fix asciinema player
timer accessible names, make Jupyter output cells keyboard-focusable,
and add missing heading hierarchy in shortcodes docs for fa/ja/zh-cn.

* feat: integrate accessibility testing with Playwright and enhance CI workflow

- Added Playwright configuration for accessibility testing.
- Implemented accessibility tests using axe-core for all English pages.
- Created a GitHub Actions workflow to automate accessibility tests on pull requests.
- Updated package dependencies to include @axe-core/playwright and @playwright/test.
- Enhanced sidebar component with data attributes for improved accessibility styling.

* fix: update base URL and improve accessibility labels across multiple languages

- Changed the base URL in Playwright configuration and CI workflow from localhost:3000 to localhost:1313.
- Added accessibility labels for screen readers in various language files, enhancing user experience for visually impaired users.
- Updated the Asciinema script to dynamically set the playback time label for better accessibility compliance.

* refactor: reorganize accessibility tests and update test directory structure

- Moved accessibility tests from the e2e directory to a new tests directory for better organization.
- Updated the test directory path in Playwright configuration.
- Refactored the accessibility test implementation to improve code clarity and maintainability.

* chore: update .gitignore to include Playwright test output directories

- Added entries for 'playwright-report/' and 'test-results/' to the .gitignore file to prevent cluttering the repository with test artifacts.

* refactor: enhance accessibility and improve focus styles across components

- Removed unused utility for focus visibility in CSS and consolidated focus-visible styles for better maintainability.
- Updated various components to use `role` attributes for improved accessibility, including menu items and buttons.
- Enhanced theme toggle and language switch components with appropriate ARIA roles and attributes for better screen reader support.
- Improved the handling of focus states in the navigation and context menus to ensure a consistent user experience.

* chore: update dependencies and enhance accessibility features

- Updated the 'serve' package version in package.json and package-lock.json for improved performance.
- Removed unused 'xml2js' dependency to streamline the project.
- Enhanced the Playwright configuration to better manage the web server setup for testing.
- Improved accessibility in the language switcher and navigation menu by refining focus management and keyboard interactions.
- Updated the back-to-top button to manage tabindex for better accessibility compliance.

* feat: enhance mobile menu accessibility and keyboard interactions

- Added ARIA attributes to manage visibility of the sidebar on mobile devices.
- Implemented focus management for the sidebar when the menu is toggled.
- Introduced keyboard support to close the menu with the Escape key.
- Improved overall accessibility for the hamburger menu and sidebar interactions.

* fix: refine mobile menu keyboard interaction and enhance navbar accessibility

- Updated the Escape key functionality to close the menu only on mobile devices.
- Added a new ARIA attribute to the hamburger menu button for improved accessibility.

i18n/nl.yaml

@@ -1,15 +1,43 @@
+# Accessibility labels (screen reader only)
+closeBanner: "Banner sluiten"
+menu: "Menu"
+mermaidDiagram: "Diagram"
+pdfViewer: "PDF-weergave"
+permalinkLabel: "Permanente link naar deze sectie"
+playbackTime: "Afspeeltijd"
+searchResults: "Zoekresultaten"
+skipToContent: "Ga naar inhoud"
+tableOfContents: "Inhoudsopgave"
+terminalRecording: "Terminalopname"
+togglePageContextMenu: "Paginacontextmenu wisselen"
+toggleSection: "Sectie wisselen"
+
+# Accessibility live-region/status text
+resultsFound: "%d resultaten gevonden"
+
+# User-facing UI text
+archives: "Archief"
 backToTop: "Terug naar boven"
 changeLanguage: "Taal veranderen"
 changeTheme: "Thema aanpassen"
+copy: "Kopiëren"
+copied: "Gekopieerd!"
+copyAsMarkdown: "Kopieer als Markdown"
+copyPage: "Pagina kopiëren"
 copyCode: "Kopieer code"
 copyright: "© 2025 Hextra Project."
 dark: "Donker"
 editThisPage: "Bewerk deze pagina op GitHub →"
 lastUpdated: "Laatst bijgewerkt op"
 light: "Licht"
+next: "Volgende"
 noResultsFound: "Geen resultaten gevonden."
 onThisPage: "Op deze pagina"
-tags: "Labels"
+more: "Meer"
 poweredBy: "Mogelijk gemaakt door Hextra"
+previous: "Vorige"
 readMore: "Lees meer →"
 searchPlaceholder: "Zoeken..."
+system: "Systeem"
+tags: "Labels"
+viewAsMarkdown: "Bekijk als Markdown"