docs(api): clarify per-version listings and latest filtering - #1735

Callers can mistake the first search result for the current version because the list documentation does not explain that results contain one record per version. Document ascending name/version-string ordering, explain that it is neither semantic-version nor publication-date ordering, and show version=latest for current records only. The clarification appears in the API guide, reference OpenAPI document, and generated documentation for both API versions.

Closes #1676.

Validation:

• CI build, lint, schema/example validation, govulncheck, and full unit/integration tests passed for aff04c2.
• Local make validate and go test ./internal/api -run '^TestOpenAPIEndpointCompliance$' -count=1 passed.
• gofmt and git diff --check passed.
• Live read-only verification reproduced superseded records without the filter and only isLatest=true with version=latest.

This changes documentation only; query behavior and result ordering are unchanged.