feat: added hasError param to OSS::TextArea

[OwenCoogan]

What does this PR do?

• Added @haserror boolean prop to explicitly control error state
• When hasError is true, the textarea shows a danger-500 border via the oss-textarea--errored class

- Backward compatibility (fallback behavior):

• Existing code using @errorMessage continues to work without changes
• If @haserror is not provided but @errorMessage exists (truthy), error state is shown
• Empty string @errorMessage does not trigger error state (only truthy values)
• Both props can be used together

- Migration:

• No immediate changes required — existing implementations continues to work
• New code can use @haserror directly for adding the border only
• Gradual migration is supported — components can use either prop or both

Related to: #

What are the observable changes?

Good PR checklist

• Title makes sense
• Is against the correct branch
• Only addresses one issue
• Properly assigned
• Added/updated tests
• Added/updated documentation
• Migrated touched components to Glimmer Components
• Properly labeled

[linear]

DRA-4481 [pubslishr-admin-web/oss-components] DraftComment block