Add OK accordion-item

[fredvisser]

Pull Request

🤨 Rationale

This PR adds the OK accordion-item component.

The component was generated with Copilot from the corresponding Stratus Storybook accordion as the source reference, then adapted to fit the OK component package structure and repository conventions.

👩‍💻 Implementation

The implementation adds the OK accordion-item web component in the OK components package, including its template, styles, appearance type, and unit tests.

It adds the matching Angular wrapper entry point for ok-angular/accordion-item, Storybook stories and MDX docs for the OK component, and a small example-client-app integration.

Important files:

• packages/ok-components/src/accordion-item/index.ts
• packages/ok-components/src/accordion-item/template.ts
• packages/ok-components/src/accordion-item/styles.ts
• packages/angular-workspace/ok-angular/accordion-item/ok-accordion-item.directive.ts
• packages/storybook/src/ok/accordion-item/accordion-item.stories.ts

🧪 Testing

Automated validation run locally:

• npm run build:components -w @ni/ok-components
• npm run lint -w @ni/ok-components
• npm run test-chrome -w @ni/ok-components
• npm run build:ok -w @ni-private/angular-workspace
• npx ng lint @ni/ok-angular
• npm run test-ok -w @ni-private/angular-workspace
• npm run build:application -w @ni-private/angular-workspace
• npx ng lint example-client-app
• npm run build:ts -w @ni-private/storybook
• npm run lint -w @ni-private/storybook

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.