fix: catch raw JSON middleware responses

[kpassito]

Summary

• Adds raw object response guidance for route, route middleware, and public makeRequest middleware returns.
• Preserves valid Response / ctx.json middleware short-circuits by serializing makeRequest middleware responses with a permissive schema.
• Adds focused regression coverage for raw object route/middleware returns, ctx.json from makeRequest middleware, and raw object makeRequest middleware rejection.

/claim #30

Verification

• ./node_modules/.bin/ava tests/bundling/make-request/make-request.test.ts tests/errors/do-not-allow-raw-json.test.ts
• ./node_modules/.bin/prettier --check src/types/winter-spec.ts tests/bundling/make-request/make-request.test.ts tests/errors/do-not-allow-raw-json.test.ts
• git diff --check
• GitHub Actions: Run Tests with Bun passed on ed6a84a

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