fix(theme):refactor theme selectors to support both html and body

[lakshmi-priya-b]

💡 What is the current behavior?

• When we try to toggle theme using 'enableToggleTheme' property in menu-component it is not working.
• 'enableToggleTheme' is internally calling 'themeswitcher'.
• Themeswitcher was modified to always target html element but selectors was still supporting only the body elements.

GitHub Issue Number: #2326

🆕 What is the new behavior?

• When we try to toggle theme using 'enableToggleTheme' property in menu-component it is working.
• Added selectors for html element as well.

🏁 Checklist

A pull request can only be merged if all of these conditions are met (where applicable):

• 🦮 Accessibility (a11y) features were implemented
• 🗺️ Internationalization (i18n) - no hard coded strings
• 📲 Responsiveness - components handle viewport changes and content overflow gracefully
• 📕 Add or update a Storybook story
• 📄 Documentation was reviewed/updated siemens/ix-docs
• 🧪 Unit tests were added/updated and pass (pnpm test)
• 📸 Visual regression tests were added/updated and pass (Guide)
• 🧐 Static code analysis passes (pnpm lint)
• 🏗️ Successful compilation (pnpm build, changes pushed)

👨‍💻 Help & support

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[gemini-code-assist]

Summary of Changes

Hello @lakshmi-priya-b, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical theming inconsistency where the themeswitcher component was designed to apply themes by modifying the html element, but the existing SCSS theme selectors were only configured to target the body element. The changes refactor these selectors to explicitly include both html and body elements for theme application, thereby enabling the enableToggleTheme functionality to work correctly across the application.

Highlights

• Theme Selector Refactoring: Modified SCSS theme selectors in theme.scss to correctly apply theme variables to both html and body elements. This resolves an inconsistency where the themeswitcher targeted html while selectors only supported body.
• Enable Toggle Theme Fix: Ensured the enableToggleTheme property in the menu-component now functions as expected by extending theme application to the html element, allowing for proper theme toggling.

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[gemini-code-assist]

Code Review

This pull request refactors the theme selectors to support applying themes to both the html and body elements, fixing an issue where theme toggling was not working correctly. The changes in packages/core/scss/theme/classic/theme.scss correctly add selectors for the html element. The fix is appropriate and addresses the problem described. I've included a couple of suggestions to improve the SCSS by using the :is() pseudo-class, which will make the selectors more concise and maintainable.

[lakshmi-priya-b]

Updated CSS class-based theme deprecation from v4.0.0 to v5.0.0 in the ix-docs.
PR-link : siemens/ix-docs#176

[nuke-ellington]

Refactoring the selector to target the HTML element will introduce other problems. Instead fix theme switcher itself.

[gemini-code-assist]

Code Review

This pull request refactors the theme switcher to use data attributes (data-ix-theme, data-ix-color-schema) on the <html> element for theme management, moving away from a purely class-based approach. This change fixes an issue with theme toggling. The logic is sound and the accompanying test updates correctly verify the new behavior. I've kept the suggestion to improve the efficiency of the toggleMode function by reducing redundant iterations over the element's class list, as it does not conflict with any provided rules.

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud