Addresses https://github.com/tscircuit/winterspec/issues/30

Summary

• Adds a shared raw-return guard so accidental raw object responses produce the intended ctx.json({...}) guidance.
• Covers route middleware returning raw objects before the final route handler path.
• Adds the follow-up null regression handling requested by automated review.

Verification

• Targeted harness confirmed route handler and route middleware raw returns produce Use ctx.json({...}) instead of returning an object directly.
• Raw Response returns still pass through successfully.
• Full npm test / npm run build were blocked locally by pre-existing dependency/setup issues (del missing and lockfile out of sync), so the PR includes focused regression evidence rather than a full-suite pass.

/claim #30