v2.18.1 — Maintenance

Patch release closing the v2.18.1 maintenance window plus spec-hygiene cleanup.

🔒 Security

• npm audit fix → 0 vulnerabilities (ajv, fast-uri, fast-xml-parser, minimatch, flatted, picomatch, brace-expansion); no --force, all within semver ranges.

📄 Fixed

• \printanswers short-answer differentiation — LaTeXFormatter.formatShortAnswer() now wraps the model answer in the exam class's \begin{solution} environment, so a short-answer-only exam's answer key reveals answers when \printanswers is uncommented (previously emitted only blank writing space).

🧹 Changed

• Gated npm run lint in CI (was ungated) + cleared 22 pre-existing ESLint errors — behavior-preserving.
• De-flaked the ai-provider rate-limit timing assertion (wall-clock vs monotonic-clock skew under parallel CI load).

📝 Docs

• Normalized status markers on 11 shipped specs to Implemented (vX.Y.Z), relocated the validate-r spec into docs/specs/, added a spec close-out step to the release checklist, and parked the rich-exam v1 acceptance gaps as .STATUS backlog.

Tests: 3,405 (3,268 Jest + 137 node:test), 143 suites.

Full changelog: v2.18.0...v2.18.1