docs: cover Ionic 9 major package upgrades

[rdlabo]

Summary

• update the portal to the iOS 26 theme v3 and Material Design 3 theme v2 documentation
• document ESLint plugin v22 for Angular 21–22 and Ionic 9, including the standalone and grouped-list rules
• document collect-icons v3 and its Ionic 9 standalone migration
• add synchronized Japanese migration guides and regenerate all affected portal pages
• pin package source links to the installed release while keeping package repositories as the English source of truth

Source documentation

The English-source corrections were reviewed, checked, and merged before regenerating this portal:

• docs: document grouped list migration eslint-plugin-rules#29
• docs: correct Ionic 9 migration guidance ionic-angular-collect-icons#10
• docs: distinguish Ionic Angular import paths ionic-theme-ios26#122
• docs: distinguish Ionic Angular import paths ionic-theme-md3#27

Validation

• npm run fmt:check
• npm run lint
• npm test — 45 contract tests and 37 Angular tests
• npm run build — 626 prerendered routes and 298 indexed documentation pages
• byte-for-byte English/Japanese fenced-code verification via the contract tests

The build retains the existing non-blocking main-bundle budget warning (426.42 kB against 425 kB).