docs: organize iOS26 theme guides

[rdlabo]

Summary

• organize non-README Markdown under lowercase docs/ paths
• document the special iOS26 markup, CSS variables, and utility classes used by the demo
• add front matter and improve public guide structure and wording
• correct the demo’s .searchbar-classic example
• replace the stale E2E notes with an implementation-aligned maintainer guide

Validation

• npm run build
• Prettier checked the changed Angular template during commit
• independent OSS documentation review approved

Documentation rollout

The related rdlabo-docs PR should be merged after this package documentation is available on main, because the portal reads English guides from GitHub raw.

[github-actions]

Playwright test results

 90 passed

Details

 90 tests across 2 suites
 1 minute, 57 seconds
 5ea098a
 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-116/

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-116/

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