fix(color): preserve Ionic color attributes

[rdlabo]

Summary

• keep Ionic color attributes effective for inset-list header labels and item-group header icons
• preserve color base, contrast, and disabled opacity for disabled colored buttons
• add comparison patterns to /main/index/item-list and /main/index/button

Verification

• targeted Prettier check
• npm run build
• demo production build
• browser computed-style checks for default and colored list and button states under Ionic 8.8.19
• manager review approved
• OSS maintainer review approved

Segment changes are intentionally excluded. Screenshot binaries are also excluded because local macOS rendering differs from Linux CI.

[github-actions]

Playwright test results

 90 passed

Details

 90 tests across 2 suites
 1 minute, 58 seconds
 4acd010
 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-ios26/pr-136/

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

[github-actions]

📊 Ionic 9 Playwright Test Report

View the detailed Ionic 9 report: https://rdlabo-dev.github.io/ionic-theme-ios26/pr-136/

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

[github-actions]

📊 Ionic 9 Playwright Test Report

View the detailed Ionic 9 report: https://rdlabo-dev.github.io/ionic-theme-ios26/pr-136/

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

[github-actions]

📊 Ionic 9 Playwright Test Report

View the detailed Ionic 9 report: https://rdlabo-dev.github.io/ionic-theme-ios26/pr-136/

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

[github-actions]

📊 Ionic 9 Playwright Test Report

View the detailed Ionic 9 report: https://rdlabo-dev.github.io/ionic-theme-ios26/pr-136/

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.

[github-actions]

📊 Ionic 9 Playwright Test Report

View the detailed Ionic 9 report: https://rdlabo-dev.github.io/ionic-theme-ios26/pr-136/

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