docs: resolve documentation audit findings for 2026-04-08

[j-shilling]

Summary

• add a dated documentation audit report at docs/audit/2026-04-08_09:26:34.md
• repair runtime, setup, guide, feature, research, and AGENTS.md drift around current routes, skip-auth behavior, and the versioned OpenAPI entrypoint
• replace the stale Cognito feature page with a branch-accurate skip-auth identity page

What Was Fixed

• runtime docs now reflect GET /health, GET /api-spec/v1/verify, POST /api/v0/education-enrollments, and POST /api/v0/veteran-disability-ratings
• setup docs now reflect the actual config surface and committed docker-compose.yml services
• contract-oriented guides now clearly distinguish checked-in OpenAPI expectations from current runtime auth behavior
• AGENTS.md now points at api-spec/v0/openapi.yaml

What Remains Unresolved

• the branch still has a contract-vs-runtime auth gap: the OpenAPI and consumer guides describe OAuth2 bearer-token usage, while the running Go service does not yet implement in-process bearer-token validation
• this PR documents that gap explicitly but does not change runtime auth behavior or Terraform-related infrastructure

Audit Report

• docs/audit/2026-04-08_09:26:34.md

Validation

• pnpm exec markdownlint-cli2 AGENTS.md README.md api-spec/README.md schema/README.md 'docs/**/*.md'