feat(22-1990n): Add CMS content pages — generated by Optimus

[voidspooks]

⚠️ AI-Generated PR — This pull request was automatically generated by Optimus. All code requires human review and testing before merging.

Are you removing or changing a registry.json entryName in this PR?

• No, I'm not changing any entryNames

Summary

Adds content-build assets for VA Form 22-1990n — Apply for VA Education Benefits Under the National Call to Service (NCS) Program.

Changes include:

• registry.json: New entry with entryName: "22-1990n", rootUrl: /education/apply-for-education-benefits/application/1990n, layout: page-react.html, breadcrumbs enabled, and vagovprod: false (feature not yet promoted to production).
• introduction.md: Introduction page content for the NCS education benefits application, including eligibility overview and entry point into the form flow.
• help.md: Help and FAQ content scoped to the 22-1990n application, covering common applicant questions about the National Call to Service program.
• error-messages.json: Form-level error message strings for validation and submission failure states specific to the 1990n flow.
• navigation.json: Navigation structure defining the chapter/page order for the 22-1990n application.

Breadcrumb trail is configured as: Home → Education and training → Apply for education benefits → Apply for NCS education benefits (VA Form 22-1990n).

• Team: Optimus / Aquia. No flipper used.

Files

• src/applications/registry.json
• content/pages/education/22-1990n/introduction.md
• content/pages/education/22-1990n/help.md
• content/pages/education/22-1990n/error-messages.json
• content/pages/education/22-1990n/navigation.json

Related issue(s)

• department-of-veterans-affairs/va.gov-team#0000

Testing done

• Code generated by Optimus AI — engineer must verify content renders locally before merging.

Acceptance criteria

• Content reviewed for plain language (8th grade reading level)
• No PII/credentials/internal URLs hardcoded
• Linting warnings addressed
• Accessibility testing performed
• Browser console contains no warnings or errors