fix: forward encode option to cookie serializer

[lprnmns]

Problem

After the cookie@2 migration, a custom encode function passed to reply.setCookie() or the serializer decorator is ignored. The resulting Set-Cookie value is emitted without the caller's encoder, despite encode being a documented cookie serialization option.

Fix

Forward the existing options object as cookie@2's serializer-options argument so its encode function is applied. Calls without encode retain their current output.

Tests

• node --test --test-name-pattern='passes encode option to cookie serializer' test/cookie.test.js — passed after the fix; the same test failed before the fix with foo=bar instead of foo=encoded.
• npm test — passed; 54 unit tests and 46 type assertions.
• npm run lint — passed.
• npm run test && npm run benchmark --if-present — passed; no benchmark script is defined.
• node --check index.js && node --check test/cookie.test.js — passed.
• git diff --check — passed.

Compatibility

The public API signature is unchanged. Existing calls without a custom encoder produce the same serialization; calls with encode now honor the documented option. The change adds no dependency or lockfile updates.

Related issue

Independent reproduction. No currently open issue or competing pull request for this behavior was found.

[Copilot]

🟢 Approval recommended

The focused fix correctly restores documented encoding behavior with regression coverage.

Pull request overview

Fixes custom cookie encoders by forwarding serialization options to cookie@2.

Changes:

• Passes options to stringifySetCookie.
• Adds regression coverage for reply.setCookie() encoding.

File summaries

File	Description
index.js	Forwards serializer options.
test/cookie.test.js	Verifies custom encoding.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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