fix: support helper and error text outside inset lists

[rdlabo]

Summary

• extract support-text handling from the inset-only layout mixin
• apply it to every ion-item inside themed ion-list elements
• preserve existing inset-list surface and nested-group styling

This lets input, textarea, and select helper/error areas render correctly in both inset and non-inset lists, including items under reorder, accordion, and radio groups.

Verification

• npm run build
• Prettier check for the changed SCSS files
• git diff --check
• inspected generated CSS selectors for the non-inset list scope

[github-actions]

Playwright test results

 78 passed

Details

 78 tests across 1 suite
 1 minute, 34 seconds
 f107343
 This detailed result covers Ionic 9 only. Ionic 8 runs against the same screenshots in a separate matrix job; check the workflow run for both results. To update the screenshots, comment with /update-screenshots.

[github-actions]

📊 Ionic 9 Playwright Test Report

View the detailed Ionic 9 report: https://rdlabo-dev.github.io/ionic-theme-md3/pr-32/

Ionic 8 runs against the same screenshots in a separate matrix job. View both results in the workflow run.