feat: support helper and error text for select, checkbox, toggle, and radio group

[rdlabo]

Summary

• add helper and error text demos for checkbox, toggle, select, and radio group
• integrate select supporting text with inset-list border handling
• render radio-group supporting text below its items while preserving iOS inset-list radii and safe-area spacing
• scope radio-group layout customization to structured inset lists

Validation

• npm run build
• cd demo && npm test -- --watch=false (35 tests)
• verified the radio helper/error layouts in the iOS demo browser

[github-actions]

Playwright test results

 14 failed
 76 passed

Details

 90 tests across 2 suites
 2 minutes, 45 seconds
 81cf096
 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.

Failed tests

chromium › screenshot.spec.ts › Screenshot Tests - All Routes › should match screenshot for radio
chromium › screenshot.spec.ts › Screenshot Tests - All Routes › should match screenshot for toggle
chromium › screenshot.spec.ts › Screenshot Tests - All Routes › should match screenshot for select:alert
chromium › screenshot.spec.ts › Screenshot Tests - All Routes › should match screenshot for select:popover
chromium › screenshot.spec.ts › Screenshot Tests - All Routes › should match screenshot for checkbox
chromium › screenshot.spec.ts › Screenshot Tests - All Routes › should match screenshot for select:modal
chromium › screenshot.spec.ts › Screenshot Tests - All Routes › should match screenshot for select:action-sheet
chromium › screenshot.spec.ts › Screenshot Tests - Dark Mode › should match dark mode screenshot for radio
chromium › screenshot.spec.ts › Screenshot Tests - Dark Mode › should match dark mode screenshot for toggle
chromium › screenshot.spec.ts › Screenshot Tests - Dark Mode › should match dark mode screenshot for select:alert
chromium › screenshot.spec.ts › Screenshot Tests - Dark Mode › should match dark mode screenshot for select:popover
chromium › screenshot.spec.ts › Screenshot Tests - Dark Mode › should match dark mode screenshot for checkbox
chromium › screenshot.spec.ts › Screenshot Tests - Dark Mode › should match dark mode screenshot for select:modal
chromium › screenshot.spec.ts › Screenshot Tests - Dark Mode › should match dark mode screenshot for select:action-sheet

[github-actions]

📊 Ionic 9 Playwright Test Report

View the detailed Ionic 9 report: https://rdlabo-dev.github.io/ionic-theme-ios26/pr-125/

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

[rdlabo]

/update-screenshots

[github-actions]

✅ Screenshots have been updated successfully!

The new screenshots have been committed to this PR.